Preclinical Operative.pdf

1st Edition

Preclinical Operative Dentistry Study Guide

Preclinical Operative Dentistry Study Guide Contact us: [email protected]

1

Contents Chapter 1: Introduction to Operative Dentistry .................................................................................... 6 Chapter 2: Principles of Tooth Preparation ......................................................................................... 23 Chapter 3: Instruments & Equipments of Operative Dentistry ......................................................... 41 Operative Dentistry Instruments ............................................................................................................... 42 Rubber Dam .............................................................................................................................................. 67 Management of Proximal Contacts ........................................................................................................... 79 Chapter 4: Dentist Posture & Patient Position ..................................................................................... 93 Chapter 5: Cavity Preparations for Dental Amalgam ....................................................................... 100 Class I Cavity Preparation for Amalgam ................................................................................................ 101 Class V Cavity Preparation for Amalgam ............................................................................................... 111 Class II Cavity Preparation for Amalgam ............................................................................................... 117 Chapter 6: Direct Restorative Materials ............................................................................................. 129 Amalgam ................................................................................................................................................. 130 Finishing & Polishing of Amalgam Restorations ................................................................................... 151 Amalgam Safety & Mercury Hazards ..................................................................................................... 163 Cavity Sealers, Liners & Bases ............................................................................................................... 174 Temporary (Provisional) Restorations .................................................................................................... 183 Glass Ionomer Restorations .................................................................................................................... 192 Composites .............................................................................................................................................. 213 Chapter 7: Cavity Preparations for Dental Composite: .................................................................... 238 Class I Composite.................................................................................................................................... 239 Class V Composite .................................................................................................................................. 246 Class II Composite .................................................................................................................................. 256 Class III Composite ................................................................................................................................. 261 Class IV Composite ................................................................................................................................. 268 Chapter 8: Pit & Fissure Sealants and Preventive Resin Restorations ............................................ 277

2

Chapter 1: Introduction to Operative Dentistry
Objectives: By the end of the lectures, the student should: 1- Understand the course description and objectives. 2- Know the course scope and outline. 3- Be familiar with references chosen and resources available. 4- Know the continuous assessment and how you will be evaluated. 5- Know the definition of operative dentistry, its indications and considerations. 6- Be familiar of the lesions affecting calcifies tooth structure: a- Dental caries. b- Erosion. c- Abrasion. d- Attrition. e- Fractures. 7- Be familiar with factors contributing to dental-caries: a- The host including: the tooth. b- Saliva. c- The micro biota in the area. d- The kind of diet consumed. 8- Be able to classify caries according to site and extent. 9- Differentiate between primary and secondary caries. 10- Understand the difference between pits, fissures, fossa and grooves. 11- Acquainted with different terminology and abbreviation used in the course. 12- Differentiate between simple, compound and complex cavity preparation. 13- Recognize the different terminology used for walls present in a prepared cavity such as (axial wall, pulpal wall, and gingival floor). 14- Identify and list the name of different line, and point angles in a prepared cavity. 15- Be able to combines the terms to describe the walls, lines, and point angles. 16- Acquainted with the cavo-surface angle and margin. 17- Be familiar to use G.V Black classification of caries lesions and restorations. 18- Define dental caries as an infectious disease. 19- Describe in a simple way how a caries lesions can develop. 20- List the possible etiological causes of the disease.

6

Operative Dentistry
Definition: It’s the art and science concerned with all procedures, whereby defects in hard tooth structures are diagnosed, eliminated, treated, prevented and the lost tooth structures are restored.


Objectives of operative dentistry: 12-

Prevention of dental caries and other causes of loss of tooth structure. Restoration of: - Health of affected teeth. - Function and occlusion. - Tooth anatomy (contact and contours…). - Esthetic. - Speech. 3- Preservation of: - Health of hard and soft oral tissues. - Arch integrity. 4- Relive of pain. 5- Prevention of recurrence.


Scope of operative dentistry: 1234-

Diagnosis or determination of the type, site and extent of the lesion. Operative procedures of designing and preparation of cavities. Restoration of lost tooth structure. Prevention of recurrence of such defects.


Types of lesions involved in tooth destruction: ABCD-

Bacterial. Mechanical. Chemico-mechanical. Endodontically treated teeth. 7

A- Bacterial dental caries: •

Definition:

Caries could be defined as a chronic disease affecting hard structures (enamel, dentin or cementum) characterized by demineralization of inorganic content and destruction of organic structures by microbial fermentation of carbohydrates from the diet leading to dissolution of hard tooth structure. •

Classification of dental caries: 1- According to the severity: A- Acute caries:  Rapid process involving a large number of teeth.  Lesion characterized by lighter color.  Sensitive area. B- Chronic caries:  Slow process.  Caries affect a fewer number of teeth and smaller in size.  Dark color. C- Arrested caries:  The caries is started then stopped because the oral environment is changed. 2- According to extent of caries: A- Incipient caries (reversible):  Is the first evidence of caries activity in the enamel.  On smooth surface enamel the lesion appear opaque white when air-dried  The lesion of de-mineralized enamel has not extended to the DEJ, and the enamel is fairly hard and still intact (smooth to touch).  The lesion can be re-mineralized if immediate corrective measures alter the oral environment, including plaque removal and control. B- Cavitated caries (Irreversible):  The enamel surface is broken (not intact) and usually the lesion has advanced into the dentin.  Re-mineralization is usually not possible.  Treatment by tooth preparation and restoration is usually indicated. 8

3- According to location: A- Primary caries:  First evidence of caries. B- Secondary caries:  Recurrent caries. •

Spread of caries:

Caries takes conical shapes in spreading in enamel and dentin. 1- Pit and fissure: - The caries in these regions usually form due to the incomplete union of the developing enamel lobes. - Complete union of lobes, 2 lobes = groove, 3 lobes = fossa. - Incomplete union of lobes, 2 lobes = fissure, 3 lobes = pit. - Caries in enamel is conical in shape, the base toward DEJ while the tip is toward the outer surface. Then, caries spread laterally along DEJ (hypo-mineralized structure). So, the base of conical shape of caries in dentin toward DEJ and the tip toward the pulp.

2- Smooth surface: - Smooth surface cavities do not begin in an enamel defect. They occur in smooth areas in surface enamel that are habitually unclean and are usually covered in plaque. - Caries spread also conical in shape. In enamel, the base is toward the outer surface while the tip toward the DEJ. Again, there is lateral spreading of caries along the DEJ. In dentin, the base is toward the DEJ while the tip is toward the pulp.

9

B- Mechanical: 1- Wear and attrition: the end result of rubbing teeth against each other or chewing hard objects. 2- Abrasion: the end result of abrasive agent rubbing against teeth, leading to notches on labial side of root surface it may occur from: a- Improper brushing techniques. b- Habit of holding pipe stem against teeth. c- Tobacco chewing. d- Vigorous rubbing between adjacent teeth. 3- Fracture: the loss of a part of the tooth due to an external blow or may split during loading force when biting on a hard object.

C- Chemico-mechanical: •

Erosion: loss of hard tooth structure due to weak chemical force coupled with weak frictional force. -

Causes: 1- Stomach acid. 2- Regurgitation habitual lemon suckers. 3- Ingestion of acid medicine.

D- Endodontically treated teeth: Vital teeth are resilient and elastic while non-vital teeth are brittle and liable to fracture.

10

NOTES: -

-

Abfraction: bulk occlusion (most affected are premolars). Fractures: complete, incomplete. Enamel hypoplasia: non hereditary, occurs when the ameloblasts are injured during enamel formation, resulting in defective enamel, it’s usually seen on the anterior teeth and first molars as opaque light brown and white areas caused by fluorosis or high fever. Amelogenesis imperfecta: hereditary, enamel defective in form or calcification, has an appearance ranging from essentially normal to extremely unsightly. Dentinogenesis imperfecta: hereditary, only affects dentin, normal enamel weakly attached and so lost early. Enamel polyarosis: the tooth looks white and less shiny because it does not have sufficient fluoride.


Areas liable to caries: 1- Self-cleansable areas: Areas which are cleansed simply by the action of tongue and cheek movement and also due to mastication. Examples:  Areas buccal and lingual above the maximum height of contour occlusally.  Areas mesial and distal above the contact area occlusally.  Cusp tip and cusp inclined planes.

2- Stagnation areas: The most liable to caries as it allows food retention. Examples:  Areas buccal and lingual in a gingival position to the maximum height of contour.  Areas mesial and distal, gingival to the contact areas.  Pit and fissures on the occlusal surface.

11

3- Less susceptible areas:  

Areas in relation to gingival sulcus. It is less susceptible due to the presence of alkaline gingival fluid which neutralizes the acidity needed for the process of caries.


Extension for prevention, enameloplasty, PRR: 

 

G. V Black proposed that restorations for smooth surface caries should be extended to self-cleansing area to prevent recurrence of caries. Later, this concept was broadened to include remaining enamel defects such as pits and fissures. This practice has virtually been eliminated. Enameloplasty refers to the removal of a shallow enamel developmental fissure or pit to create a smooth, saucer-shaped self-cleansing surface.


Classification of cavities: 1- According to surface anatomy: a- Pit and fissure cavities. b- Smooth surface cavities.

2- According to the number of involving surfaces: a- Simple cavity: Involving one surface. b- Compound cavity: involving two surfaces. c- Complex cavity: Involving more than two surfaces.

12

3- According to G.V. Black classification: a- Class I Restorations: -

All pit and fissure restorations. Restorations on occlusal surface of premolars and molars. Restorations on occlusal two thirds of the facial and lingual surfaces of molars. Restorations on lingual surface of maxillary incisor.

b- Class II Restorations: -

Restorations on the proximal surfaces of posterior teeth.

c- Class III Restoration: -

Restorations on the proximal surfaces of anterior teeth (without incisal angle).

d- Class IV Restorations: -

Restorations on the proximal surfaces of anterior teeth involving the incisal edge.

e- Class V Restorations: -

Restorations on the gingival third of the facial or lingual surfaces of all teeth (except pit and fissure lesions).

f- Class VI Restorations: -

Restorations on the incisal edge of anterior teeth or the occlusal cusp heights of posterior teeth.

Notes: -

Cavity: defect in the enamel of teeth resulting from pathological process. Prepared cavity: It is a form created into a tooth to meet certain biomechanical requirements necessary to retain and support the tooth and the restorative material for which it is designed.

13

Rule I:  The surrounding walls of the prepared cavity take the names of the adjoining or corresponding tooth surfaces.

Rule II:  The floor of the prepared cavity occlusal to the pulp, and at a right angle to the long axis of the tooth is called pulpal floor.

 If the pulp is removed and the cavity is extended to involve the pulp, this floor is called subpulpal floor.

 The floor of the prepared cavity near the gingival tissues and lateral to the pulp is called the gingival floor.

Rule III:  The wall in axial surface parallel to the long axis and approximates the pulp is called the axial wall.

Rule IV:  All line angles are formed by the junction of two walls; or one wall and floor, and named by combining the names of the sharing walls.

Rule V:  All point angles are formed by the junction of two walls and floor, and named by combining the names of the sharing walls and floor.

Lines & Point angles Class I = 8 Line Angles, 4 Point Angles& 5 walls Class II = 11 Line Angles & 6 Point Angles& 6 walls Class III = 6 Line Angles & 3 Point Angles& 4 walls Class IV = 11 Line Angles & 6 Point Angles& 6 walls Class V = 8 Line Angles & 4 Point Angles& 5 walls 14


Tooth preparation terminology: 1- F = facial. 2- D = distal. 3- P = pulpal. 4- L = lingual. 5- M = mesial. 6- G = gingival. 7- A = axial. 8- DF = disto-facial line angle. 9- DP = disto-pulpal line angle. 10- DL = disto-lingual line angle. 11- Mf = mesio-facial line angle. 12- MP = mesio-pulpal line angle. 13- ML = mesio-lingual line. 14- DFP = disto-facial- pulpal point angle. 15- FP = facial- pulpal line angle. 16- MFP = mesio-facial- pulpal point angle. 17- DLP = disto-lingual- pulpal point angle. 18- LP = lingual-pulpal line angle. 19- MLP = mesio-lingual- pulpal point angle. 20- AFP = axio-facial- pulpal point angle. 21- AF = axio-facial line angle. 22- AFG = axio-facial-gingival point angle. 23- FG = facial-gingival line angle. 24- AG = axio- gingival line angle. 25- LG = lingual-gingival line angle. 26- ALP = axio-lingual-pulpal point angle. 27- AP = axio-pulpal line angle. 28- AL = axio- lingual line angle. 29- AGL = axio- gingivo- lingual point angle.

15


Tooth preparation walls:  Internal wall: An internal wall is a prepared (cut) surface that does not extend to the external tooth surface.

 Axial wall: An axial wall is an internal wall parallel with the long axis of the tooth.  Pulpal wall: A pulpal wall is an internal wall that is perpendicular to the long axis of the tooth and occlusal of the pulp.

 External wall: An external wall is a prepared (cut) surface that extends to the external tooth surface. Such a wall takes the name of the tooth surface (or aspect) that the wall is towards.

 Floor (or seat): A floor (or seat) is prepared (cut) wall that is reasonably flat and perpendicular to the occlusal forces that are directed Occluso-gingivally (generally parallel to the long axis of the tooth). Examples are the pulpal and gingival walls. Such floors may be purposefully prepared to provide stabilizing seats for the restoration, distributing the stresses in the tooth structure, rather than concentrating them. This preparation increases the resistance form of the restored tooth against post-restorative fracture.

 Enamel wall: the enamel wall is that portion of a prepared external wall consisting of enamel.  Dentinal wall: the dentinal wall is that portion of a prepared external wall consisting of dentin, in which mechanical retention features may be located

16


Cavo-surface angle and margin: The cavo-surface angle is the angle of tooth structure formed by the junction of a prepared (cut) wall and the external surface of the tooth. The actual junction is referred to as the cavosurface margin. The cavo-surface angle may differ with the: -

Location on the tooth. Direction of the enamel rods on the prepared wall. The type of restorative material to be used.

The cavo-surface angle is determined by projecting the prepared (cut) wall in an imaginary line and the unprepared enamel surface in an imaginary line and noting the angle opposite to the cavo-surface angle.

17


Revision: 1- Wear or loss of the tooth surface by chemico-mechanical action is: a- Erosion. b- Attrition. c- Abfraction. d- Abrasion. e- Fracture. 2- When caries occurs at the junction of a restoration and the tooth. It’s called: a- Acute caries. b- Incipient caries. c- Secondary caries. d- Arrested caries. 3- When a smooth surface carious lesion appears as opaque white, with a fairly hard and intact enamel surface, your decision to treat such a lesion will be: a- To try and remineralize the lesion since it is reversible. b- To prepare and restore the lesion with appropriate restoration. c- To seal the affected area with a sealant. d- To monitor the lesion. e- To perform prophylactic odontotomy. 4- A carious lesion which appears dark in color is most probably: a- Acute. b- Incipient. c- Chronic. d- Primary. 5- Causative factors of dental caries include: a- Saliva factors. b- Cariogenic diet. c- Bacterial biofilm. d- Saliva factors, Cariogenic diet & Bacterial biofilm.

18

6- According to black's classification of cavities, a maxillary incisor may show the following classes: a- I, III & V. b- II, III & V. c- I, IV &V. d- I, III, IV, V & VI. 7- Smooth surface lesion in proximal surface of teeth includes: a- Class II, IV & V. b- Class II, III & IV. c- Class I, II & III. d- Class III, IV & V. e- Class II, III & VI. 8- Mechanical wear of incisal and occlusal surface as a result of functional or Para-functional mandibular movements is considered: a- Erosion. b- Attrition. c- Abfraction. d- Abrasion. e- Fracture. 9- Cavities involving cusp tip 23& incisal edge 21 can be considered as: a- Class III. b- Class II. c- Class V. d- Class IV. e- Class VI. 10- The Gingival wall is located: a- Apical to the interproximal contact. 11- A proximal carries lesion on the cervical of tooth number 26 is considered: a- Simple class II. b- Simple class V. c- Simple class III. 19

d- Compound class III.

12- A proximal carious lesion on the facial of tooth number 26 is considered: a- Simple class V. b- Simple class II. c- Simple class I. d- Simple class III. e- Compound class III. 13- The principle bacterial agent involved in the caries process is: a- Lactobacillus Acidophilus. b- Streptococcus Sangvis. c- Streptococcus Salivarins. d- Streptococcus Mutans.

20

Student Notes:

21

22

Chapter 2: Principles of Tooth Preparation
Objectives: 1- Each student should know the definition of tooth preparation. 2- Each student should recognize the need of tooth preparation. 3- Each student should distinguish the objectives of tooth preparation and identify the factors affecting the tooth preparation either general factors, patient factors or restorative material factors. 4- Each student should define conservative of tooth preparation. 5- Each student should know biological and mechanical principles of tooth preparation, and recognize its importance during each stage of cavity preparation. 6- Each student should distinguish initial and final stages of tooth preparation. 7- Each student should recognize, define and know the criteria of each step of the initial tooth preparation which includes: Step 1: outline form and initial depth. Step 2: primary resistance form. Step 3: primary retention form. Step 4: convenience form. 8- Each student should recognize, define and know the criteria of each step of final tooth preparation which Includes: Step 5: removal of any remaining enamel pit or fissure, infected dentin and/or old Restorative material, if indicated. Step 6: pulp protection, if indicated. Step 7: secondary resistance and retention forms. Step 8: procedures for finishing the external walls of the tooth preparation. Step 9: final procedures: cleaning, inspecting and sealing. 9- Each student should know the additional concepts in tooth preparation for Amalgam restorations. 10- Each student should realize the additional concepts in tooth preparation for composite restorations. 11- Each student should distinguish the main differences between bolt preparation of amalgam and Composite restorations.

23

Tooth Preparation
Lecture Outline:   

Objectives of tooth preparation. Factors affecting tooth preparations. Stages and shapes of tooth preparations.


Definition of tooth preparation: The mechanical alteration of a defective, injured or diseased tooth to best receive a restorative material that will re-establish a healthy state for the tooth, including esthetic corrections where indicated, along with normal form and function.


Objectives of tooth preparations:    

Remove all defects and provide necessary protection to the pulp. Extend the restoration as conservatively as possible. Form the tooth preparation so that under masticatory forces the tooth or restoration will not fracture or the restoration will not be displaced. Allow for functional and esthetic placement for restorative material.


Operative treatment goals: Treatment should preserve and restore:  Teeth morphology.  Function.  Esthetics.  Harmonious relationships.  Pulpal health. Get the smallest possible cavity for demonstrable removal of all caries with water coolant.

24


Essential of cavity preparation:   

Remove all caries and defects and give the necessary pulp protection. Locate the margins of the restoration as conservatively as possible. Form the cavity so that the tooth and / or restoration won’t fracture and the restoration won’t be displaced. Restore form, function and esthetics to the tooth.




Factors affecting tooth preparations: 1- Diagnosis:     

The reason for placing the restoration in the tooth. Periodontal and pulpal status. Esthetic factor. Relationship with other treatment plans. The risk potential of the patient for other dental caries.

2- Knowledge of dental Anatomy:   

Gross picture of the tooth internally and externally must be visualized. The thickness of the enamel, dentin and position of the pulp. Relation to other supporting tissue.

3- Patient factors:   

The patient’s knowledge and appreciation for good dental health. Patient’s economic status. The patient age.

4- Conservation of tooth structure:   

Preservation of the vitality of the tooth by avoiding the application of poor or careless operative procedure on the tooth. Restorations should be made as small as possible. Small tooth preparations result in restorations that have little effect on both inter-arch & intra-arch relationships as well as esthetics. 25

5- Restorative material factors:   

Amalgam vs. Resin Composite. The ability to isolate the operating field. The extension of the problem (caries).


Principle of cavity preparation:    

Gain access to caries. Removal of all carious lesions. Cut away all significantly unsupported enamel (undermined enamel). Extended margins so that they are accessible for instrumentation and cleaning.


Principle of cavity preparations:   

Biological Principles. Mechanical Principles. Esthetic Principles.


Classification: (G.V. Black Classification) Black suggested that it was necessary to:  Remove additional tooth structure to gain access and visibility. Note: (this is called extension for destruction & this is wrong because we have to be conservative)  Remove all trace of demineralized enamel and dentin from the floor, walls and margins of the cavity.  Make room for insertion of the restorative material in efficient bulk to provide strength.  Provide mechanical interlocking retentive designs.  Extend the cavity to self-cleansing areas to avoid recurrent caries.

26

 What are class I lesions?     •

Caries in occlusal pits and fissures of posterior teeth. Caries in the occlusal 2/3 (two-thirds) of the facial and lingual of posterior teeth. Caries in the lingual pits of maxillary incisors. Palatal pit of upper incisor. NOTE: MOD = Mesio–Occluso-Distal cavity

Recognizing class I caries:     

Softening at the base of a pit or fissure. Opacity surrounding the pit or fissure and enamel appearance changes when dried. Softened enamel that can be flaked away by explorer. Brown gray enamel (caused by lateral spread of caries into dentin). Radiographic evidence.

 Class II: 

The lesions involving the proximal surfaces of the posterior teeth with access established from the occlusal surface.

 Class III: 

The lesions involving the proximal surfaces of anterior teeth which may involve a labial or a lingual extension but does not include the incisal edge.

 Class IV: 

The lesions involving the proximal surfaces of anterior teeth which include the incisal edge.

 Class V: 

The lesions involving the cervical third of all teeth, including the proximal surface of posterior teeth where the marginal ridge is not included in the cavity preparation.

27


Design and preparation of cavities: The design and preparation of cavities are based on Black’s principles that have been determined and re-applied with importance directed towards protection of tooth in preparation rather than only on the material. Each diseased tooth has an individual cavity form determined by caries involvement, morphology of tooth and its location on the oral cavity  leading to new conservative cavity designs.


Steps in the Cavity Preparation: If it’s not extensive caries (given by GV Black): 1- Obtaining outline form. 2- Obtaining primary resistance form. 3- Obtaining primary retention form. 4- Obtaining convenience form. 5- Removal of remaining carious dentin. 6- Obtaining secondary resistance and retention form. 7- Providing pulp protection. 8- Finishing of enamel walls and margins. 9- Performing the toilet of the cavity


Steps in the Cavity Preparation: If it’s extensive caries (modified by GV Black): 1- Convenience Form. 2- Outline Form. 3- Caries Removal. 4- Resistance Form. 5- Retention Form. 6- Finish. 7- Debridement.

NOTE: Never cut an important structure such as the stress bearing area (cusps & marginal ridge).

28


Stages and Steps of Tooth Preparation: (Same steps on two stages in order to simplify)

 Initial Stages: 1234-

Outline form and initial depth. Primary resistance form. Primary retention form. Convenience form.

 Final Stage: 12345-

Removal of any remaining defected dentin. Pulp protection if indicated. Secondary resistance and retention forms. Procedures of finishing external walls. Final procedures: cleaning, inspecting & sealing.


Initial tooth preparation stages: I.  

Outline form and initial depth: Cavity margins placed in the positions they will occupy in the final preparation. Initial depth is 0.2 – 0.5mm into dentin (in pit & fissure) and 0.2 – 0.8mm for extension onto the root surface (and in smooth surfaces) Notes:  We shouldn’t stop at the DEJ and we have to reach the dentin because the DEJ is very sensitive (due to anastomosis of dentinal tubule).  The depth in smooth surface enamel (0.2- 0.8) is more than in pits & fissures (0.2 - 0.5) because the thickness of the enamel is lesser in the pits& fissures.

29

•

General Principles: 1- All friable and or weakened enamel should be removed. 2- All faults should be included. 3- All margins should be placed in a position to afford good finishing of the restoration margin.

•

Factors to consider: 12345-

•

Consideration for establishing proper outline form and initial depth: 123456-

•

Extent of the carious lesion, defector faulty old restoration. Esthetic considerations. Occlusal relationships. Adjacent tooth contours. Cavo-surface marginal configurations.

Preserving cuspal strength. Preserving marginal ridge strength. Minimizing Facio-lingual extensions. Using enameloplasty. Connecting two close faults or cavity preparations less than 0.5mm apart. Restricting the depth of the cavity preparation into dentin.

Considerations for proximal surfaces: 12345-

Margins into sound tooth structure. Avoid terminating margins on extreme eminences. Create sufficient access for manipulation. Axial wall 0.2-0.8 mm into dentin. Preserve gingival margins (always supra gingival, unless if the decay extend to the sub gingival area). 6- Preserve buccal and lingual margins. Note: Cavo-surface angle = 90 & it should be rounded.

30

II.

Primary resistance form:



It is the shape and placement of the cavity walls that enable the tooth and restoration to withstand Masticatory forces (along the axis of the tooth) without fracture.

•

Fundamental principles involved in obtaining primary resistance form:

1- Box shaped: o All internal right angles should be rounded to prevent stress and rotation of the restoration. o Flat floor. o Restrict the extension of the external wall. 2- Cap weak cusps and envelope weakened tooth structure to prevent fracture. 3- Provide the right thickness according to the type of material. 4- Bond the material to the tooth structure when possible. Note: we must be conservative thus only the carries should be removed.

NOTE: Dentin Bridge: Thickness of dentin from the pulp to the floor of the cavity Dentin Ledge: depression in dentin to remove the caries done by round large bur, low speed & minimal pressure or by spoon excavator.

•

Minimal thickness of restorative materials for adequate wear and resistance to fracture: Amalgam Gold Porcelain Composite

•

1.5 mm 1 mm 2 mm variable

Factor affecting resisting form: 1- Remaining tooth structure: affect need and type of resistance form. 2- Type of restorative material: amalgam vs. composite.

31

III.

Primary retention form:

It's the shape or form of the cavity preparation that can resist displacement or removal of the restoration from tipping or lifting forces e.g. gum. •

NOTE: Retention includes: slots, retentive grooves & dovetails

Types of restorations:

1- Direct restoration:  Used in the clinic e.g. Amalgam & Composite.  We need to make an occlusal convergence. A- Amalgam:  Class II &III: mechanical retention with converging walls.  Class V: retention grooves. B- composite:  Mechanical retention with enamel/dentin bond. 2- Indirect restoration:  In the clinic and lab.  Diverging wall with taper \__/ •

Types of retentions: 1- Macro mechanical means of retention: retentive groves, Convergence e.g. Amalgam and Metallic. 2- Micro mechanical means of retention: by the usage of acid itching to make selective pores and bonding e.g. composite. 3- Frictionary retention (both amalgam and composite). Notes:  Retentive grooves are used in class II & class V.  The restoration is most susceptible to displacement in class II & class IV.

NOTE: Caries detection is done by: • X-ray • Vision (discoloration) • Pain (if under restoration) • Consistency by prop

32

IV.    

Convenience Form: It is the shape or form that the cavity preparation allows for adequate observation, access and ease of operation in preparation and restoration of the cavity. Extension of proximal and or buccal or lingual wall to access deeper parts of the cavity. Occlusal divergence on cast restoration (class II preparation). Extending proximal preparations beyond the contact area.


Final tooth preparation stages: V. 

VI. 



VII.  

Removal of caries and old restoration material: States of dentin inhibited by cariogenic bacteria: A. Infected dentin: soft and discolored. B. Affected dentin: hard and discolored (the carries is arrested).

pulp protection: Liners ≤ 0.5 mm, which are: o Protective barrier against noxious agent. o Thermal insulation. o Secondary dentin. o Combat gap formation. Bases ≥ 0.5 mm, which are: o Protection against any irritation. o Thermal insulation.

secondary resistance and retention forms: Mechanical features e.g. locks, groove, cover, extension, skirt, beveled margins, pins, slots, Amalgam pins Cavity wall conditioning features: o Acid itching enamel wall. o Placing bonding agents or glass Ionomer on dentin walls.

33

VIII. 

IX.

procedures for finishing the external walls: Objectives of finishing the cavity walls: o Create the best marginal seal. o Provide a smooth marginal junction. o Give maximal strength to the tooth and restorative material at and near the margin.

Cleaning, inspecting and sealing:   

Flushing the cavity with warm water to remove debris. Lightly air drying the cavity. Using a sealer when indicated (e.g. dentin bonding agent).

34

Amalgam vs. Composite

Pulpal depth

Amalgam Include fault, break proximal & gingival contacts, include all suspicious areas Uniform 1.5 – 2mm

Axial depth

Uniform 0.2 – 0.5mm into DEJ

Cavo-surface angle

90 degrees buccal and lingual

Remove fault, not always uniform Remove fault, not always uniform >90 degrees buccal and lingual

Bevels

None

Only for esthetics and retention

Texture of prep walls

Smooth

Rough

Primary retention

Convergence occlusally

Enamel/dentin bond

Secondary retention

Grooves, slots, pins

Grooves, convergence

Resistance form

Flat floors perpendicular to the occlusal forces

Base indications Liner indications

2mm distance between amalgam and pulp Ca(OH) over direct pulp cap

Flat floors perpendicular to occlusal forces for large preparations None Ca(OH), GI, Flowable composite

Sealer

GLUMA or bonding

Bonding agents

Outline Form

35

Composite Include fault, break gingival contact, seal suspicious areas


Revision: 1- Grooves, slots, locks & coves are considered as: a- Retentive means in prepared cavity. b- Resistance means in prepared cavity. c- Convenience means in prepared cavity. d- Finishing means of prepared cavity. 2- The mesial & distal walls in class I cavity preparation for amalgam must diverge occlusally to satisfy: a- Outline form. b- Resistance form. c- Retentive form. d- Convenience form. 3- A simple class V preparation on a molar has: a- 4 walls, 4 line angles & 4 point angles. b- One internal wall & 3 external walls. c- 5 walls, 4 point angles & 8 line angles. d- One internal wall & 5 external walls. e- 5 walls & 5 point angles. 4- One of the following features is not a macro-mechanical retention: a- Acid etching. b- Dovetail lock. c- Grooves. d- Undercuts in dentin. 5- According to black's classification of cavities tooth #25 may show the following classes: e- I, II & V. f- II, III & V. g- I, IV &V. h- I, III, IV, V & VI.

36

6- The best geometrical design of the prepared cavity to resist fracture under masticatory forces: a- Converge wall cavity design. b- Diverge wall cavity design. c- Saucer-shape cavity design. d- Box-shape cavity design with relatively flat floor. 7- Dentin bridge can be defined as: a- Dentin left between the prepared cavity pulpal floor and the pulp. b- Dentin connecting between two different parts of the prepared cavity. c- Dentin left intact in the deepest portion of the prepared cavity. d- Dentin removed during cavity preparation. 8- Unsupported enamel in amalgam preparation should be: a- Protected by the restoration. b- Left intact. c- Finished at 90 degrees. d- Removed. e- Finished in acute angle 9- Conservative cavities modified form Black’s principles have the advantages of: a- Decreasing fracture vulnerability & less display of restorations. b- Decreasing fracture vulnerability of restorations. c- Less display of restorations. d- Being cheap. 10- Retention needed for composite restoration is: a- Micro-mechanical retention. b- Macro-mechanical retention. c- Micro & Macro-mechanical retention. d- Frictional retention. 11- It is the shape or form that is given to the cavity to allow for adequate observation, access and ease of operation in preparation and restoration of the cavity: a- Resistance form. b- Convenience form. c- Retention form. d- Outline form.

37

12- Oblique ridge in maxillary molars should be preserved, unless: a- Caries. b- Undermined. c- Fissured. d- None of above. e- All of above. 13- A simple class III on proximal surface of molars has: a- 4 walls, 4 line angles & 4 point angles. b- 4 walls, 8 line angles & 4 point angles. c- 5 walls, 8 line angles & 5 point angles. d- 5 walls, 8 line angles & 4 point angles. e- 5 walls, 6 line angles & 3 point angles. 14- Removing all sharp line angles is considered as: a- Resistance form. 15- Dentin ledge is proposed in deep caries to fulfill the requirement of: a- Outline form. b- Resistance form. c- Retention form. d- b & c. e- b & a.

38


Student Notes:

39

40

Chapter 3: Instruments & Equipments of Operative Dentistry

41

Operative Dentistry Instruments
Objectives: By the end of the lectures, the student should: 1- Know what materials hand instruments are made of. 2- Know different parts of cutting and non-cutting hand instruments. 3- Understand the rationale of angulating hand instruments. 4- Be familiar with different nomenclatures and classifications for hand instruments (descriptive and numeric). 5- Know the design, function, cutting modes of a hatchet, chisel, spoon and gingival marginal trimmers. 6- Be able to differentiate between different marginal trimmers (e.g. Mesial from distal) and different angle formers. 7- Be able to differentiate hatchets from chisels. 8- Understand and use the Black’s numeric classifications (three and four number formulas), and when both are used. 9- Be familiar with the function and design of non-cutting instruments such as (amalgam carriers, condensers, carvers, burnishers, plastic instruments, spatulas, mirrors, explorers, periodontal probes, and forceps). 10- Know the common instruments grasps, and be able to describe them. 11- Know the type of hand pieces (hp) used in dentistry. 12- Know the type of contra-angle available (high and low speed). 13- Be familiar with speed ranges for both high and low speed and their indication of use 14- Know different types of heads used with the contra-angle hp. 15- Be familiar with the components of dental burs their function, and types: a- Shank (differentiate between types). b- Neck. c- Head [two major types: bladed and abrasive, different shapes (e.g. Round, fissure...)]. 16- Know the basic shapes of burs and how they are numbered. 17- Know the different materials burs are made of. 18- Be familiar with the indication of use of common dental burs (e.g. Round, inverted cone...). 19- Know the different modifications of the bur head. 20- Be familiar with finishing burs (12 or more flutes) and their uses. 21- Know hazards of cutting instruments, and how to prevent or avoid them.

42

Operative Dentistry Instruments
The instruments that are used in Operative Dentistry are classified into: 1- Cutting instrument. 2- Exploring instrument. 3- Restoring instrument.


Cutting instruments:  

Definition: They are the instruments used for cutting of the tooth structure. Classified into: A- Hand cutting instrument. B- Rotary cutting and Rotary abrasive instrument. C- Ultrasonic instruments.


Hand cutting instruments:  Are made from: 1- Shaft which is grasped by the hand of the operator and has the following features: a- Usually standardized in size. b- Usually serrated for better handling of instrument. 2- Blade which has the cutting edge. 3- Shank which connects between the Shaft and the Blade and usually tapers from the shaft towards the blade.

 Classification of the hand instrument depending on the number of Angles: 1234-

Straight hand instrument (shaft, shank and blade in one line). Mon-angle hand instrument (shank has 1 angle). Bin-angle hand instrument (shank has 2 angles). Triple angle hand instrument (shank has 3 angles).

Q: why do we have more than 1 angle? A: for better accessibility to the area of operation. 43

 Contra angle hand instrument: •

Definition: 2 angles opposite to each other.

•

Advantages: 1- Better stability. 2- Better accessibility.

 Hand cutting instruments can also be classified into: 1- Long handle instrument: shaft, shank and blade are one piece. 2- Cone, Socket instrument: Shank and blade are one piece and the shaft is another piece and they are screwed together by a screw.

I.

•

Advantages: Cheaper to replace when broken.

•

Disadvantages: 1- Less stable. 2- Limited to mirror.

Instrument Nomenclature: G.V black described a way to name the hand instruments according to its name: 1- The Order: denotes the PURPOSE of the instrument e.g. excavator, scalar. 2- The Suborder: denotes the POSITION and MANNER of the use of the instrument e.g. push, pull. 3- The Class: describes the FORM of the blade e.g. hatchet, chisel. 4- The Angle (Sub-Class): denotes the NUMBER of ANGLES in the shank e.g. bin-angle, triple angle. N.B. Naming of the instrument usually moves from 4 to 1 e.g. bin-angle hatchet push excavator. Q: The Purpose of the instrument represents? A: The Order.

44

II.

Instrument Formula: 1- Ordinary formula:  

The bevel (edge of the blade) is perpendicular to the long axis of the blade. Consists of 3 figures:

1- The width of the blade in tenths of millimeters. 2- The length of the blade in millimeters. 3- The angle between the blade and the long axis of the shaft in degrees. Example: -----11 (1) -----6 (2) -----12 (3) ----(1) Width of blade = 1.1 mm (2) Length of blade = 6mm (3) Angle between the blade and long axis of shaft = 12°

2- Special formula:  

The bevel (edge of the blade) is not perpendicular (acute) to the long axis of the blade. Consists of 4 figures:

1234-

The width of the blade. The angle between the cutting edge of the blade and the long axis of the shaft. The Length of the blade. The angle between the blade and the long axis of the shaft.

Example: -----15 (1) -----95 (2) -----8 (3) -----12 (4) ----(1) (2) (3) (4)

Width of blade = 1.5 mm Angle between the edge of blade and long axis of shaft = 95° Length of blade = 8 mm Angle between the blade and long axis of shaft = 12°

45

III.

Bevels: To use the hand cutting instrument it has to have a bevel and is named according to the number of bevels e.g. it is called uni-bevel when it has 1 bevel, bi-bevel when it has 2 bevels on opposite sides or it can have a circular (or oval shaped) bevel (all around the blade) and is called circumferential bevel.

IV.

Types of Hand cutting instruments: A. Excavators. B. Chisels. C. Special forms of chisels.

1- Excavators: Are designed for the excavation and removal of carious dentine and for shaping the internal parts of the cavities. •

Types of Excavators: 1- Hatchet Excavator:  Used for the removal of HARD decay.  Used for the shaping of the internal part of the cavity.  Bi-bevel.  The blade is in one line with the long axis of the shaft. 2- Hoe Excavator:  Used for the removal of HARD decay.  Used for the shaping of the internal part of the cavity.  Uni-bevel.  The blade is perpendicular (at right angle) with the long axis of the shaft.  If the bevel is away from the shaft it is distal and if the bevel is near the shaft it is mesial.

46

3- Spoon Excavator:  Used for the removal of SOFT decay.  The blade is oval (or semi-circular) in shape and has concavity.  Has circumferential bevel (around the edge).  Lateral cutting instrument.  “Double ended instrument” one end to the right and the other to the left.  Made in pairs. 4- Discoid (Disk-Like) Excavator:  Same as Spoon excavator except that its blade is circular in shape. 5- Cleioid (Claw-Like) Excavator:  Same as spoon excavator except that its blade has a pointed end.  Used in carving of amalgam and excavating decays.

2- Chisels:   •

Are hand instruments used for the cutting of enamel. Usually beveled on one side.

4 Types: 1- Straight chisels:  Have straight blade in line with the handle and shank.  The cutting edge is on one side only with the bevel of the blade making a right angle with the long axis of the shaft.  Uni-beveled. 2- Mon angle chisel:  Similar to straight but blade has 1 angle. 3- Bin angle chisel:  Similar to straight but blade has 2 angles.

47

4- Triple angle chisel:  Similar to straight but blade has 3 angles.

3- Special forms of chisels: Designed to perform specific functions •

Types: 1- Enamel hatchet:  The cutting edge is in the form of a bevel parallel to the shaft.  Used for splitting or cleaving undermined enamel for buccal and lingual wall in proximal cavities. 2- Gingival (cervical) marginal trimmer:  These are 2 pairs of this instrument consisting of a set of 4.  The cutting edge of one pair makes an acute angle with the edge of blade furthest from the handle. 3- Angle formers:  Like straight but the edge of the blade makes an acute angle (nearly 80 degrees).  Used to cut line and point angles. 4- Wedel steadt chisel:  Like straight but with slight vertical curvature in its shank.  Used for cleaving undermined enamel and shaping of the wall.

48

V.

Instrument grasp: 1234-

Pen grasp. Inverted pen grasp. Palm and thumb grasp. Modified palm and thumb grasp.

1- Pen grasp: 



The instrument is held between the thumb and the first and second fingers, the third finger is used for rest. Advantages: 1) More flexibility of movement. 2) Less power needed.

2- Inverted pen grasp:  

The same as the pen grasp but the hand is rotated so that the palm is facing upwards. Usually used in upper teeth.

3- Palm and thumb grasp:  

It is a power-grasp where the handle of the instrument is held in the palm of the hand and grasped by 4 fingers. The thumb is resting on adjoining surface.

4- Modified palm and thumb grasp:   

The handle of the instrument is in contact with tips of the 4 fingers on one side and the hand is half closed. The thumb is used for resting. Not frequently used. Permits greater freedom of movement.

49

VI.

Rests:  Fingers not used in grasps are used to: 1- Stabilize the working hand. 2- Keep the instrument confined to preparation (control of instrument). 3- Prevent injury to soft tissue.

 Rest should be: 1- Near the same arch and quadrant operated on. 2- As near as possible to the area of operation. 3- Must be on hard structure.

VII.

Guards:   

Are finger positions of the free hand. To steady parts being operated on. Protect them from injury in case of slipping of the instrument.


Restoring Instruments: 1- Condensing instruments:    

For condensation of plastic restoration. Have different shapes and sizes e.g. triangular, rounded, rectangular… The face either smooth or serrated. Serrated is better because it increased the surface area but will clog with residual amalgam.

50

2- Carvers:  

Used to shape amalgam and composite. Types: 1- Cleioid, discoid carvers. 2- Walls carvers. 3- Hollenback carvers. 4- Interproximal carvers. 5- Sickle shape carvers.

3- Burnishers: 



Types: a- Round. b- Egg or ovoid. Functions: a- To make smooth surface. b- Compacting. c- To bend cast gold near the margins.

4- Plastic filling instruments: 1- Used with plastic restorations. 2- To carry and shape tooth colored restorations. 3- It may be plastic or metal.


Types of explorers: 1234-

Straight, for occlusal surface. Curved or sickle shape, for proximal surface. Briault’s, for proximal surface. Right angle, for proximal surface.


Mixing surface: 1- Glass slab used for mixing cements. 2- Paper pad used for mixing calcium hydroxide and composite.

51


Dappendish:    

Small glass, plastic or metal dish. Has large depression in one end and small depression in the other end. Has several colors. Used to hold pastes, liquid and alcohols.


Mirrors:   



Size ranges from 3/4 to 1 5/8 inch. Is cone-socket instrument. Types: 1- Plain. 2- Magnifying. Uses: 1- Indirect vision. 2- Retraction of lips and cheeks. 3- Illumination of dark areas.


Tweezers:   

Has two blades and handle. It may be locked or unlocked. Used to grasp materials and cottons.


Mixing instruments (spatula):  

Has flat and wide blade. Made from stainless steel, ivory or plastic.


Rotary tools:  



For removal of tooth structure. Types: A. Burs, which are rotary cutting tools that have a bladed cutting head. B. Stones which are abrading tools. C. Discs. Diamonds: o Are sometimes called burs but are correctly named diamond abrasive point.

52


Dental cutting burs:  Every bur will have three parts: i. ii. iii.

The head: the position carrying the cutting blades. The neck: the position connecting the head to the attachment part. The shank: the attachment part (the position that will be engaged within the hand piece).

 Types of burs: • According to their mode of attachment to the hand piece, dental burs can be classified as either: 1- Latch type (for low speed). 2- Friction grip type (for high speed). •

Also according to hand piece they are designed for: 1- Contra angle burs (short shank). 2- Straight hand piece burs (long shank).

•

Or classified according to the length of the head to: 1- Long. 2- Short. 3- Regular.

•

They can also be classified according to their use into: 1- Cutting burs:  Have 6-8 blades and are separated by clearance spaces. 2- Finishing burs:  Have 12-40 blades and are condensed to each other – no spaces. 3- Polishing burs:  The head is completely smooth.

53

•

According to their shape and size they may be classified as: 1- Round burs:  They are numbered from ¼, ½, 1, 2, to 10.  They are round in shape and used for initial tooth preparation, placement of retentive grooves and removal of caries. 2- Wheel burs:  They are numbered from 14 to 15.  They are wheel shaped, used for placing grooves and for gross removal of tooth structure. 3- Inverted cone burs:  They are numbered from 33 ¼, 33 ½, 34, 35 to 39.  Used mainly for cavity extension and establishing wall angulation and retention forms.

4- Plain cylindrical fissure burs:   

•

They are numbered from 55 to 59. The bur teeth can be cut parallel to the long axis of the bur which is designed “straight”. Or cut obliquely to the long axis of the teeth (for better unclogging) which are called spiral.

According to materials: 1- Steel bur:  Has low melting point.  Has low hardness.  Limiting its use for cutting dentin and with low speed. 2- Carbide bur:  Has high melting point.  Has high hardness.  Used for cutting enamel and with high speed.  Brittle.

54


ISO numbering system: In 1986, a new numbering system was approved by ISO International Organization for Standardization the system covers all sizes and materials of the bur.  1st number: material of the head.  2nd number: type and length of the shank.  3rd& 4th numbers: shape of the head.  5th number: size of the head.

 Design of dental burs: a) b) c) d) e) f)

Bur tooth. Rake angle. Land. Clearance angle. Tooth angle. Flute or chip space.

A. Rake angle: 

The angle between the face of the bur tooth and a radical line from the center of the bur to the blade. It’s either -ve, +ve or 0 (radical).

Radius

Positive Ranke Angle

Radial Or "0" Rake Angle

55

Negative Rake Angle

B. Clearance angle:  

The angle between the back of the tooth and the work. If a land is present : i. Primary clearance (
C. tooth angle:  

Between the face and the back. If a land is present: i.

Cutting efficiency of rotary instruments: It is the ability of the bur to remove a maximum amount of tooth tissue with a minimum of effort and time involved.

 Factors influencing cutting efficiency: A. Bur design & manufacture : 1- tooth angle:  The angle between the face &the back.  ↓tooth angle ↑ efficiency. 2- rake angle:  +ve rake angle ↑ effective cutting (better with carbide).  Radial rake angle  effective cutting (less than +ve).  -ve rake angle  effective cutting (less than +ve& -ve). 3- Chip space:  Space between two successive teeth.  ↑ Chip space ↑ cutting efficiency.

56

4- Clearance angle:  The angle between the back &the work.  ↑ Clearance angle ↑ cutting efficiency &↓ dulling of the bur. 5- Land:  The plane surface following the cutting edge.  Bur with land ↑ effective cutting. 6- number of teeth or blades:  Normal: 6-8 blades.  Less no. of blades: o ↑ Force on each blade. o ↑Thickness of chip. o ↓ Clogging tendency. o Cooler operating. o ↑ Tendency for vibration. 7- Shape of blade:  Cross cut bur: o More effective than plane cut specially with low speed. o Increase chip space & less clogging. 8- Type of blades:  Straight blades less cutting than spiral. 9- Shape of the bur:  Inverted come more efficient than fissure bur under similar conditions. 10- Run-Out:  It refers to the eccentricity or maximum displacement of the bur head from its axis of rotation while the bur turns.  Average clinically acceptable run out is about 0.023mm. 11- heat treatment:  Steel burs must be heat treated to increase its cutting efficiency.

57

12- finish of the flutes:  Burs should be well finished during manufacturing for better cutting efficiency. 13- composition of the bur:  Carbides are more efficient than steel. B. Design of hand piece: 1- Friction:

 Heat production due to friction between moving parts of hand piece specially turbines.  ↑ Friction ↓ cutting efficiency. 2- Torque:  Ability of a tool to withstand the lateral cutting without decreasing speed. It depends on the type of bearing used.  ↑ Torque ↑ cutting efficiency. 3- Vibration:  Eccentric movement that occurs during cutting by the bur which may be due to: o Binding of the bur. o Badly constructed bur. o Wearing of hand piece part.  ↑ Vibration ↓cutting efficiency. 4- Frequency & amplitude:  ↑Frequency &↓ amplitude is the best. 5- Turbine hand piece:  Water & air turbine are the most efficient for cutting. C. Speed:

 ↑ Speed ↑ cutting efficiency.

58

D. Tissue to be cut:

 Dentin is easily cut than enamel. E. Time:

 ↑ Duration of cutting ↑ cutting efficiency.  But by time, dullness of the bur &↓cutting efficiency. F. Temperature:

 ↑ Temperature ↓ cutting efficiency.


Speed ranges & uses: 1- Low speed bur ranges below 6,000 R.P.M used for:      

Cleaning of teeth. Removing of hard caries with round bur. Smoothing of cavity preparation. Finishing & polishing of restoration. Margination of the gold restoration. Finishing procedure.

2- Medium or intermediate speed range from 6,000 – 100,000 R.P.M. used for:  

Cavity preparation. Placement of retentive grooves and bevels.

3- High speed at 100,000 R.P.M. used for:   

Removing old restoration. Obtaining outline form. Cusp reduction.

59


Revision: 1- Carbon steel bur has: a- Low melting point. b- High hardness number. c- High melting point. d- Used to remove the enamel. e- Used only with high speed. 2- A small round bur is used to: a- Remove caries. b- Gain access to cavities. c- Lateral extension of the cavities. d- Finishing of walls of the cavities. 3- When approaching caries close to the pulp in deep cavity rotary cutting instrument should be applied for caries remove and cavity preparation refinement in the range of: a- Ultra high speed. b- High speed. c- Medium speed. d- Low speed. 4- An instrument with the number 14-85-10-12 means: a- Angle between working edge and long axis of handle is 85 degrees. b- Angle between blade and working edge is 12 degrees. c- Length of the blade 1 mm. d- Length of the blade 14 mm. e- Length of the blade 12 mm. 5- If you are using a low speed hand-piece, then you would be using: a- Friction grip shank burs. b- Friction latch shank burs. c- Latch straight shank burs. d- Latch type shank burs.

60

6- A discoid is used for: a- Removing undermined enamel. b- For hard carious dentin. c- For the excavation of soft caries. 7- In ordinary instrument formula, the second figure indicates: a- Width of the blade in mm. b- Width of the blade in 1/10 mm. c- Blade length in mm. d- Blade angle in centigrade. 8- Removal of deep caries lesions can be done by: a- Pear shape bur. b- Large tapered fissure bur. c- Large round bur. d- Large fissure bur. e- Inverted cone bur. 9- The spoon excavator is designed: a- To remove undermined enamel. b- To remove hard varieties of caries. c- To remove soft carious dentin. d- A claw like instrument of enamel. 10- Rotary cutting instrument should be applied for caries remove and cavity preparation refinement in the range of: a- Ultra high speed. b- High speed. c- Medium speed. d- Low speed.

11- The type of instrument grasp with the greatest power is: a- Pen grasp. b- Palm & thumb grasp. c- Modified palm & thumb grasp. d- Palm thrust grasp.

61

12- Chisels are used mainly to cut: a- Enamel. b- Dentin. c- Cement. d- Carious dentin. 13- Gingival marginal trimmer is: a- A set of 2 instruments. b- A set of 4 instruments. c- A set of 6 instruments. d- A type of excavator. 14- A discoid cleioid is used for: a- Removing undermined enamel. b- For hard carious dentin. c- For the excavation of soft caries. 15- The method of choice to peel-off caries is by: a- Caries dye. b- Large round bur. c- Polymer bur. d- Sharp spoon excavator. 16- The ideal instrument for beveling the enamel margin of gingival walls is: a- Enamel hatchet. b- Gingival marginal trimmer. c- Enamel chisel. d- Sharp spoon excavator. 17- Which hand instrument effectively planes the enamel of buccal and lingual walls of class II cavity preparation: a- Gingival marginal trimmer. b- Straight chisel. c- Enamel hatchet. d- Hoe excavator. e- Angle formers.

62

18- Retention grooves in class II amalgam cavity preparation are prepared using: a- Inverted cone bur. b- Long tapered fissure bur. c- Pear shaped bur. d- Cylindrical fissure bur. 19- A cleiod-discoid is considered: a- A cutting instrument. b- A carving instrument. c- A burnishing instrument. d- A pre carving burnishing instrument. e- An excavator. 20- Cutting Burs have: a- 6 - 8 blades. b- 12 - 16 blades. c- High tendency to clog. d- No clearance angle. 21- If the working end of cutting dental instrument is right angle to the long axis of the handle the instrument most probably: a- Hatchet. b- Chisel. c- Spoon. d- Hollenback carver. e- Burnisher. 22- If u decided to use the high speed hand piece to do your operative project the one you pick is: a- Friction grip bur. b- Latch type bur. c- Friction-latch type. d- Straight hand piece bur. e- None of the above

63

23- If the working end of the cutting dental instrument is not at right angle to the long axis of the handle the instrument most probably: a- Hatchet. b- Chisel. c- Spoon. d- Hollenback carver. e- Gingival Marginal Trimmer. 24- One of the following is a major bur: a- Flame bur. b- Wheel bur. c- Inverted bur. d- Brush bur. 25- Inverted cone bur cause: a- Undermined enamel. 26- The average range of the low speed hand piece is: a- 10,000-25,000. b- 20,000-25,000. c- 10.000-35,000. d- 15,000-35,000. e- 500-15.0000. 27- If u are holding your pen to answer these Q. using your thumb and index which tip of your finger rest on top of your pen then this grasp is called: a- Pen grasp. b- Modified pen grasp. c- Thumb grasp. d- Palm thumb grasp. e- Index thumb grasp.

64


Student Notes:

65

66

Rubber Dam

67

Rubber Dam
Methods of moisture control: 

     

Suction (Oral evacuating systems): a- High volume suction (H V Evacuator). b- Low volume suction (L V Evacuator) or Saliva ejector. Absorbants (moisture Control & Isolation of teeth). Compressed air. Local anesthetics. Antisilagogues. Elector-surgery. Rubber dam (moisture Control & Isolation of teeth).


Definition of moisture control: It’s excluding sulcular fluid, saliva and gingival bleeding from the operating field.


What is a Rubber Dam? The rubber dam is a flat thin sheet of latex/ non-latex that is held by a clamp and frame that is perforated to allow the teeth that will be worked on to protrude through the perforations in the sheet while all the other teeth are covered and protected by the rubber dam


Rubber Dam:   

Introduced in 1864 by S C Barnum. Available in four gauges. Standard of care for Endodontic& Adhesive Dentistry.

 Advantages: 12345-

Dry, clean operating field. Access and visibility. Improved properties of dental materials. Protection of the patient and operator. Operating efficiency. 68

 Disadvantages: 1234567-

Some patients feel discomfort with dam in place. The patient cannot speak easily (one side conversation). A few patients dislike the rubber dam, others panic. The clamped tooth may feel sensitive for some hours after. Rubber dam removal. Patient may be allergic to latex. It takes time for application & removal (only for beginners)

 Criteria for Acceptable Rubber Dam Placement: 12345-

Moisture control is established. Adequate exposure of teeth to provide visual access and adequate finger rests. Dam is stabilized and secure with an absence of tissue damage. Clamp is properly ligated. Dam is properly inverted.

 Rubber dam Setup (armamentarium): 12345678-

Rubber dam material. Rubber dam punch. Rubber dam clamp (retainer). Rubber dam clamp (retainer) forceps. Rubber dam frame (holder). Rubber dam napkin. Lubricant. Modeling compound, Ligature, Scissor & Wedgets.

69

1. Rubber Dam Material:  

       

     

Natural rubber latex. Pre-Cut Sheets: o 6 x 6 inch size … Adults. o 5 x 5 inch size … Pediatric Uses. Bulk Rolls … either 5 or 6 inch wide. Colors - Light, Dark, Green, Blue, Fiesta, Pink, and Purple - Fruit Scented. Shelf life-2 years if kept refrigerated. Thin (0.15 mm) in endodontic treatment – heavy contacts, posterior teeth. Medium (0.20 mm) universal. Heavy (0.25 mm) retraction  for operative. Extra heavy (0.30 mm) retraction. Special heavy (0.35 mm) bleaching- mainly anterior teeth, blue in color. N.B: Thicker RD retracting the tissue with compression & resist tearing, give more contrasts and recommended for class V in conjunction with clamp # 212. Beige endo. & pedo (because it is somewhat transparent!). Green & violet adhesive dentistry (contrast color), shade before use please! Blue bleaching mainly anterior teeth. Gray most common in operative. N.B: The lighter the colorthinner. RD is available in dark and light colors & dull and shiny faces. Dull side  facing the occlusal side for easily passage and more light reflection.

 Non-Latex Rubber Dam Material:       

100% Latex-Free. Powder-Free. No rubber scent. Tear resistance similar to latex. Color reflective. Minimum 3-year shelf life. Hygenic brand – 6x6 inches, Medium (.010 inch [.025mm]) - .010 inches.

70

2. Rubber dam punch: A. Hole positioning guides. B. Types of rubber dam punches.

A. Hole Positioning Guides:   

   

•

Teeth as a guide: (mark teeth with a felt pen). Templates: Stiff plastic template with holes indicating where the teeth should be marked. Rubber dam stamps: o Ink on gloves. o One size fits nobody. R D stamps available for average adult and pediatric arch sizes RD applied on maxillary teeth, the 1st hole in the upper central incisor 1 inch from superior border of the dam. RD applied on mandibular teeth, 1st hole in the lower central incisor in the inferior border of the dam. Distant between holes= distances between centers of 2 adjacent teeth =about 6.3 mm: o Excessive distance wrinkle RD. o Little distance  stretch dam & leakage. o Correct distance  intimate RD adaptation around teeth, retract interdentally tissue. Factors affecting position of the holes: 1234-

Position of the tooth to be isolated. Curvature of the jaw. Condition of the gingiva: excessive recession needs close holes. Type of RD: Thin RD needs small holes.

B. Types of Rubber Dam Punches:  

Ainsworth-type punch. Ivory-design punch.

71

3. Rubber Dam Clamp (Retainer):      

Consists of four prongs and two jaws connected by a bow. Anchors to most posterior tooth to be anchored (usually). Different sizes and shapes for various clinical situations. Both ‘Winged’ and ‘Wingless’ variants. Winged: small projections allow it to be mounted on dam prior to application. Wingless (W): applied directly to tooth.

 Winged Clamp:    

The “wings” are placed into the hole in the dam first, and then both are placed on the tooth together. Provide extra retraction of the R.D. Allows attaching the dam to retainer. They interfere with placement of matrix band.

 Wingless Clamp: This type of clamps is placed on the tooth first, and the dam stretched around it.

 Distinguishing feature of R D Clamps: abcde-

Winged or wingless (letter W before). Distance of the clamp bow to the distal surface of the tooth. Length of the clamp jaw (premolar vs. molar). Contact zone bucco-lingual. Clamp jaw with or without curvature in apical direction (letter A after).

 Rubber Dam Clamp Designations: ‘W’ = Wingless. ‘A’ = Designed for partially erupted teeth. ‘D’ = Distal Extension

72

 Commonly used R D Clamps:     

W7 or 7 for mandibular molar. W8 or 8 for maxillary molar. W2 or W4 for premolars. W14A or 14A for partially erupted molars. 212 for class V anterior teeth (Retractors).

As a General Role: For limited isolation, include one tooth posterior & 2 teeth anteriorly to the operating tooth & bow must be distal to the tooth.

 Cervical clamp (212) placement of class V:   

Heavy RD. Facial placement of the hole. Lingual jaw is 1st placed under cingulum then facial 0.5- 1 mm gingival to cervical line.

 Clamp Ligature: Ligature: An important safety step that makes it possible to retrieve a clamp should it accidentally become dislodged and then inhaled or swallowed by the patient.

73

 Anchors (other than retainers):    

Waxed dental floss or tape (ligature) to anchor the anterior one or more teeth with short clinical crown (no need to clamp). Interproximal retainer (wooden wedge, small piece of RD, elastic cord Wedgets. Low –fusing modeling compound, sometime used to secure the retainer to the tooth and prevent its movement during operative procedure specially class V. Anterior anchor interproximal retainers, while posterior anchors clamps.

4. Rubber Dam clamp forceps:  Function: placement & removal of clamp from tooth.   

With distal tip (e.g. Ivory).

Without distal tip (e.g. Martin). Lock at opening position (locking handle kept upward for better release due to work of gravity).

5. Rubber Dam Frame (Holder):     

Stabilizes and stretches the dam so it fits tightly around the teeth and out of the operator's way. Available in plastic and metal frames. Young’s frame (U-shape metal frame). Nygaard-Ostby plastic frame. Woodbury plastic frame.

74

6. Rubber Dam Napkin: 1234-

Prevent skin contact with rubber to reduce allergic reaction. Absorb saliva at the corner of the mouth. Act as a cushion. Aid in cleaning the patient lip on removal of the dam.

7. Lubricant:    

It’s applied to the under-surface of the punched holes area. It facilitates passing the dam through proximal contacts. Shaving cream or soap slurry (no greases or petroleum oil or Vaseline!). Lubricant: Water-soluble lubricant placed on the underside of the dam to help the dam material slide over the teeth and through the interproximal spaces.

8. Important required accessories:     

Waxed dental floss : Tape much preferred over floss Scissors. Wedgets. Wooden wedges. Lips and facial skin moisturizing.

75


Revision: 1- The rubber dam frame is used to: a- Hold the clamp in position. b- Keep the patient mouth open. c- Keep the rubber dam material stretched. d- Isolate a group of teeth. 2- The largest hole in rubber dam punch is used for: a- The largest tooth. b- All molar teeth. c- Each rubber dam material application. d- Tooth with clamp on. 3- The rubber dam materials used have different color according to: a- Type of procedure. b- Patient preference. c- Dentist eye comfort. d- Thickness needed. 4- The clamp that is used on maxillary molar teeth: a- W7. b- W8. c- W4. d- W2. 5- W7 clamp is used on: a- Mandibular molar.

76


Student Notes:

77

78

Management of Proximal Contacts
Objectives: 12345-

Understand the importance of formation of proper contacts & contours. Be acquainted with the functions of dental matrices. Describe the techniques and the rationale of matricing for amalgam restorations. Select the proper technique for matricing of posterior composite restorations. Differentiate between different types of retainers, matrices & select the suitable type for different clinical situations. 6- Identify the importance of using a wedge, the different types of wedges and their methods for application.

79

Management of proximal contacts
Definitions:  

Proximal contact area: it denotes the area of proximal height of contour of mesial or distal surface of the tooth that touches its adjacent tooth in the same arch. Contour: the vertical curvature of the buccal (facial) and lingual surface. Note: the main goal of using a matrice is to restore the contact and contour (to give it its original shape).

 According to the general shape of contours and contacts teeth can be divided into three types: 1- Tapering type. 2- Square type. 3- Ovoid type.

 Types of Contours: 1- Under contoured. 2- Over contoured. 3- Normal contour.

 Procedures for the formation of proper contacts and contours:  

Intraoral procedure: Tooth movement, matricing Extra oral procedure: Wax pattern, cast adjustment


Matricing  

Matrix: anything that holds and gives form to something. Dental matrix: a temporary wall of resistance replacing the missing wall or walls to pack the restorative material until setting.

80

 Functions: 1- It serves as a temporary wall (or walls) of resistance during condensation of plastic restorative materials. Necessary force of condensation can be applied safely against walls to produce adaptation. 2- Establishes optimal contacts and contours to the restoration and prevents marginal over hangs. 3- It maintains restoration form until it hardens. 4- It keeps the gingival tissues and rubber dam away from the cavity margins during restoration. 5- It provides an acceptable surface texture for the restoration.

 Ideal requirements of matrix: 123456789-

Easy to introduce and remove. Complete encirclement of tooth surfaces. Thin to enable positive contact (0.0016-0.0020 inch in thickness). Rigid to permit forceful condensation. Smooth to produce a smooth restoration. Compatible with restorative material. Stabilized firmly. Properly extended (one mm above occlusal and below cervical margins of preparation). Conforms to larger occ. & narrower cervical diameters to prevent overhangs.

 Selection of suitable matrix system: Methods to optimize contour and contacts.

 Parts of matrix: 1) Band:   

A piece of metal or polymeric material used to support and give form to the restorative material during its insertion and hardening. Materials used are: Stainless steel – cellulose acetate [cellophane] – cellulose nitrate [celluloid] – Polyacetate [Mylar]. Dimensions: o Width = 3/6inch, 1/4inch, 5/16inch. o Thickness = 0.001-0.002 inch.

81

2) Retainer: 

This is a device by which the band be maintained in its designated position and shape, the retainer may be a mechanical device, dental floss, a metal ring or impression compound.


Ivory no.1 This matrix consists of a stainless steel band which encircles one proximal surface of the tooth.

 Indications: For restoring a unilateral class II cavity especially when the contact on the unprepared side is very tight.


Ivory no. 8 This matrix consists of a band that encircles the entire crown of the tooth.


Tofflemire matrix  

This is also referred to as the UNIVERSAL MATRIX. The matrix is usually preferred for most class II amalgam restorations.

 Indications: 1- For class I cavities with buccal or lingual extension. 2- For restoring class II cavities on one or both proximal surfaces of a posterior tooth.

 Advantages: 1- Ease of use. 2- Produces good contact and contour for most amalgam restorations. 3- Rigid and stable.

82

 Disadvantages: 1- Does not provide optimum contact and contour for posterior composite restorations. 2- Not useful for extensive class II restorations.

 Components of the Tofflemire retainer: 1234-

Set screw - locks the band. Rotating spindle - adjust size. Slide - placement of the band. Head - different exits.

 Assembly of Tofflemire: 1234-

Loop exits opposite to the cavity. Retainer lies in the buccal vestibule. Narrow side of the band faces the gingiva. Slot in the slide also faces the gingiva.


Compound Supported Matrix  Indications: 1- For restoring class II cavities involving one or both proximal surfaces. 2- For complex situations like pin-amalgam restorations.

 Advantages: 1- Highly rigid and stable. 2- Provides good access and visibility for placing the restoration. 3- Most efficient means of reproducing contact and contour.


T-Band Matrix This is a PREFORMED T SHAPED stainless steel matrix band without a retainer.

83


Precontoured Matrix   

It consists of small, precontoured dead soft metal matrices ready for application to the tooth. They are selected according to the tooth to be restored &wedged to adapt the gingival contour. Following this the band is held in place by a flexible metal ring called Bitine ring.

 Indications: 1- For class II cavities involving one or both proximal surface of a posterior tooth. 2- For both amalgam and composite restorations.

 Advantages: 1- Ease of application. 2- The metal ring affords slight tooth separation. 3- Provide better proximal contours for posterior composite restorations.

 Disadvantages: 

Expensive.


Copper Band Matrix    

Copper band of asserted sizes make excellent matrices. These are cylindrical in shape & can be selected according to the diameter of the tooth to be restored. The band is softened by heating to redness in a flame &quenching in water. After that the band can be stretched &shaped with contouring pliers.

 Indications: 1- For badly broken down teeth especially those receiving pin-amalgam restorations. 2- For complex situation like class II cavities with large buccal or lingual extension.

 Advantages: 

Provide excellent contour. 84

 Disadvantages: 

Time consuming.


Auto Matrix The auto matrix is a retainer-less matrix system.

 Components of the Auto Matrix: 1- Auto Matrix band:  Available in thickness of 0.0015-0.0020 inch.  Maybe of three widths narrow (small = 3/6 inch, medium = 1/4 inch, wide = 5/6 inch).  Maybe selected according to the height of the tooth to be restored. 2- Automate 2 tightening device: this is used to adjust the loop of the band according to the circumference of the tooth to be restored. 3- Shielded nippers.

 Indications: 

For complex amalgam restoration where one or more cusps are to be replaced.

 Advantages: 1- Convenient to use. 2- Improves visibility due to lack of interference from a retainer. 3- Auto-lock loop can be positioned facially or lingually rapid application.  Disadvantages: 1- Bands are flat and difficult to burnish. 2- Cannot develop proper contacts and contours. 3- Expensive.


Clear Plastic Matrix  

Transparent plastic strips are employed as matrices for tooth colored restoration as they allow light to be transmitted during polymerization of composite resins. These may be cellophane or Mylar strips, which may be contoured using operating pliers.

85


Transparent Cervical Matrix   

These are commercially available transparent plastic crown forms. They are available in various sizes &contours for anterior teeth. A suitable crown form can be selected for the prepared tooth & trimmed to fit 1 mm past the prepared margins.


Proximal Wedges:  Introduction:     

Wedges: devices that create rapid separation during tooth preparation and restoration. Made of wood. Different types & sizes. Wider base towards gingiva. Customize.

 Functions of wedges: 1- Assure the close adaptability of the matrix band to the tooth. 2- They prevent the restorative material from impinging on gingival embrasure thus ensuring proper health of the interdental papilla. 3- Define the gingival extent of the contact as well as the facial and the lingual embrasures. 4- They separate the teeth to compensate for the thickness of the matrix band. 5- A traumatically retract the rubber dam and gingiva from the gingival margins of proximal tooth preparations there by producing a temporary hemostasis 6- Assure the immobilization of the matrix band arranged facio-lingually and cervico-occlusally during insertion of restorative material. 7- Prevent overhang.

 Types of wedges: A. Wooden wedges:  Are made from soft wood like pine or hard wood like oak.  Usually preferred as they: 1- Are easy to trim. 2- Adapt well. 3- Absorb moisture and swell to provide adequate stabilization to the matrix band. B. Plastic wedges. C. Light transmitted wedges. 86

 Special situation: 1- Use of 2 wedges to adapt well to the margins. 2- Modify wooden wedge by shaping it.

 Problems of wedge misplacement: 1- High contact (wedge too high). 2- Proximal concavity (wedge not gingival enough). 3- Overhang (not adapting the band).

 Proximal contact function: 1- Stability of the dental arch. 2- Prevention of food impaction.

 Contact location: 123456-

Junction of middle and occlussal thirds. 1 mm below marginal ridge. Surrounds by embrasures. Located more facially in lower. Posteriors. Located more lingually in upper posteriors.

87

Hazards of faulty contact size and location Correct Contact

•

Correct contact. Note position and form of contact and form of embrasures around contact. Also note that mesial and distal pits are below (gingival of) proximal marginal ridges.

Broad contact faciolingually

•

Interproximal tissue is over-protected and will not receive proper stimulative massage from excursion of food. Extra breadth of contact prevents food from scouring the embrasures

•

•

Contact too far gingivally

Creates a wider space between the two proximal surfaces in an occlusal direction. Sticky foods are likely to become packed into this space and eventually force the teeth apart. • Impinges upon interproximal tissue. • Frequently observed in amalgam restoration. • Crest of gingival is far from contact and predispose the proximal surface to caries. • Prevents food from being pushed into embrasures. Buccal /lingual embrasures are narrow, produce inefficient mastication.

Contact too far incisal/occlusal

Contact too far buccal/lingual

Loose contact

Food independent in open contact area develops gingival problems and caries.

Broad contact occluso-gingivally

• • •

88

Sticky foods are likely to be held. Encroaches upon gingival tissue. If proximal caries occurs, it will be farther gingivally.


Revision: 1- A patient with 36 OD prepared amalgam cavity with a tight mesial contact, the best type of matrix retainer to be used is: a- Tofflemire matrix. b- Ivory no. 1. c- Ivory no. 8. d- Automatrix. 2- Pre-wedging is done before preparation of class II cavity in order to: a- Prevent iatrogenic damage to the adjacent sound tooth. b- Allow visualization of the carious lesion. c- Prevent over contouring of the final restoration. d- Allow excessive instrumentation of the proximal cavity. e- Prevent damage of the contact area of the prepared tooth. 3- The correct sequence of removing a Tofflemire system after finishing an amalgam restoration is: a- Wedge, retainer and then the band. b- Wedge, the band and then retainer. c- The retainer, the band and then the wedge. d- The retainer and the band are removed as one piece, followed by the wedge. e- Wedge first then retainer and the band are removed as one piece. 4- When placing a wedge against a matrix before restoration: a- Always place it occlusal to the margin of the restoration. b- Always place it gingival to the margin of the restoration. c- Always place it round wedges in deep proximal lesions. d- Always place anatomical wedges in shallow proximal lesions. e- Always place triangular wedges from the lingual embrasure. 5- The large rotating spindle of the Tofflemire retainer is responsible for: a- Securing the band to the retainer. b- Tightening or loosening the band. c- Directing the band straight, right or left. d- Placing the band on the tooth.

89

6- The slot of the Tofflemire head should be facing: a- Occlusal direction. b- Mesial direction. c- Distal direction. d- Gingival direction. e- The opposite diagonal quadrant. 7- When placing a wedge against a matrix before restoration: f- Always place it occlusal to the margin of the restoration. g- Always place it gingival to the margin of the restoration. h- Always place it round wedges in deep proximal lesions. i- Always place anatomical wedges in shallow proximal lesions. j- Always place triangular wedges from the lingual embrasure.

90


Student Notes:

91

92

Chapter 4: Dentist Posture & Patient Position

93

Dentist Posture & Patient Position
Balanced home operating position: The inter-relation of the jointed segments of the body of the operator.


Position: The way a person holds him/herself: 1- Upright- while standing or moving on the feet. 2- Seated- at work or at rest. 3- Supine- at rest.


Operating benefits: 1234567-

Superior instrument control. Increased accuracy. Improved perception. Superior concentration. Fewer distractions. Fewer operating decision during procedures. Increased efficiency.


Physical and psychological benefits to the operator: 1- Better vision with less eye fatigue (reduces tension, irritability, headache and lowers blood pressure and/or pulse rate). 2- Increased perception and kinesthetic senses. 3- Better posture creating better physical and psychological health (more physical energy and more personal comfort). 4- More gentle treatment noticed by patients. 5- Improved patient comfort (physical and mental). 6- Relaxed performance. 7- Improved auxiliary performance.

94


Operating posture: 123456-

Thighs parallel to the floor. Feet flat on the floor. Neck and back relatively straight. Forearms parallel to the floor. This result in an operating distance of roughly fourteen inches. The lower visual eye fields should be used in an effort to offset the strain usually felt in the neck when the head is continually tilted forward.


Posture position movements: To maintain correct POSTURAL and POSITIONAL conditions, the performer (operator)MUST be able to control 5 variables: 1- Move about patient head between 12:00 and 10:00 position. 2- Adjust patient head in dorso-ventral axis form -20 and +8 degrees. 3- Move patient's head, right or left, as much as 45 degrees. 4- Achieve the unrestricted opening and closure of patient's mouth from 12mm to 44mm. 5- Raise and lower patient to a position compatible with that of the seated operator's correct working posture.


Patient position:  







Total body support. Patient should have direct access to the chair. o Chair height should be low. o Backrest should be upright. o Armrest elevated to allow the patient to get into the chair. The headrest cushion is positioned to support the head and elevate the chin slightly away from the chest. o In this position, neck muscle strain is minimal and swallowing is facilitated. The most common patient positions are: 1- Supine position: patient head, neck, knee and feet are approximately on the same level. 2- Reclined 45 degrees. Advantages of comfortable patient position: 1- Less muscular tension. 2- More capable of cooperating with the dentist.

95


General consideration:     

  

When operating on maxillary teeth, maxillary occlusal surface should be directed perpendicular to the floor. When operating on mandibular teeth, mandibular occlusal surface should be directed 45 degrees to the floor. The face of the operator should not come in close proximity to that of the patient. The teeth being treated should be at the same level as the operator's elbow. The operator should not hesitate to rotate the patient's head backward or forward or from side to side to accommodate the demands of access and visibility without sacrificing the good operating posture of the dentist. Maintaining an appropriate working distance from the patient is important for the operator to master. Minimize body contact with the patient. The operator should not rest his forearms on the patient. The patient's chest should not be used as an instrument tray.


Instrument grasp: Modified pen grasp: 1- The instrument is held with the same fingers as the pen grasp except that the pad of the middle finger is placed on the top of the shank of the instrument with the index finger. 2- Provides more control and strength in some procedures. 3- Decrease operator fatigue. 4- It's used to hold instruments that have angled shanks.

96


Revision: 1- Regarding the dentist and patient positions, the following is true: a- When operating on the mandibular arch. Mandibular occlusal surfaces should be bcde-

perpendicular to the floor. Teeth being treated should be at the same level as operator’s elbow. Patient’s chest can be used as an instrument tray. Head of the patient should always be lower than his/ her feet. Never try to rotate the patient head towards the operator.

97


Student Notes:

98

99

Chapter 5: Cavity Preparations for Dental Amalgam

100

Class I Cavity Preparation for Amalgam
Objectives: 12345678-

Be acquainted of different designs of class I cavity preparation. Know the difference between simple, compound and complex class I cavity. Be able to list and identify different outline forms. Know the proper resistance forms of amalgam cavities. Compare between conservative and improper extended cavity. Identify the proper retentive features used in class I cavity for amalgam. Explain of the no Need of convenience form in class I. Be able to identify and differentiate between the proper, correct and incorrect cavity walls and margins and what were the causes of differences. 9- List and know the different orientations of enamel rods, and what consequences can develop for leaving undermined enamel. 10- List and explain why we do toilet to the cavity and how to check it. 11- Know, list and explain how gaining access is done using a suitable sized round bur; the direction of cutting is parallel to the long axis of the tooth until reaching the dentin. The cutting is done through the weakest portion of the tooth, i.e. central or proximal triangular fossa. 12- Know, list and explain how lateral extension of the cavity to include all pits and fissures is done using inverted cone bur. Proximally, the extension is done midway between the marginal ridge and the proximal triangular fossa. Buccally and lingually, the extension should not exceed the inter-cuspal distance. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 13- Know, list and explain how finishing of cavity walls and margins is performed using cylindrical fissure bur. The bucco-lingual dimension of the cavity should be 1/4 - 1/3 the inter-cuspal distance, while the depth of the cavity should be from 0.5-1 mm beyond the DEJ. 14- The directions of the buccal and lingual walls of the finished cavity should be converging occlusally, while the distal and mesial walls should be diverging occlusally. The cavo-surface angle of the finished cavity should be 90°.

101

Class I Cavity Preparation for Amalgam
Indications:      

Moderate to large restorations. Restorations are not in a highly esthetic area. Restorations that have heavy occlusal forces. When good isolations cannot be achieved. As foundations. As abutments.


Contraindication:    

Esthetic areas. Small to moderate cavities which can be well isolate. Small class VI lesions. Class III, IV and V in anterior teeth.

1. Class I cavity preparation:  Characters of caries:    

Two opposite cones with their base at the DEJ. Cone shaped spread in enamel with the base at the DEJ and small openings. Cone shaped spread in dentin with the base at the DEJ. Rapid lateral spread at DEJ.

 Designs of class I cavity preparation: •

It may be: 1234-

Class I simple cavity. Class I extension cavity (compound). Class I facial pit cavity (simple). Class I lingual cavity in anterior teeth.

102

 Clinical technique / tooth preparation: Outline form:    

Place margins in sound tooth structure. Cavity margins must be placed at contact – free areas. Conserve ridges involved in occlusal contact (oblique ridge). Include all defective pits and fissures.

 Outline form: •

Should include:

 All carious and undermined enamel.  All pits & fissures. •

Should be:

 Extended to area self-cleansable.  Multi curved without any sharp line angles to prevent stress concentration. •

Bucco – lingually:

 Should not extend beyond the inter–cuspal line except if there is caries.  Minimal width of the cavity about 1/4 – 1/3 the inter–cuspal distance. •

Mesio – distally:

 Should be extended midway between the triangular fossa and the crest of the marginal ridge.

103

 Resistance form:         

Maximum conservation of sound tooth structure. CSA = 90 degrees. Minimal cavity width. Flat and smooth pulpal floor parallel to the occlusal plane and perpendicular to the long axis of the tooth. Roundation of axial line angles. Providing bulk through the cavity depth for Amalgam strength (0.5 – 1mm beyond the DEJ). Preserve adequate bulk of mesial and distal marginal ridges (minimum of 1.6 mm width): flared. Extend lateral walls minimally. Round all internal line angles (prevent stress areas).

 Retention form:  

Only against axial displacement, in the form of mechanical undercuts in dentin, by converging the cavity walls. Create walls that are parallel to each other, or slightly convergent in an occlusal direction.

 Convenience form: 

No need for convenience in class I cavity preparation as it is easily seen and instrumented.

 Finishing of enamel wall:       

The enamel wall should take the same direction of enamel rods without undermining. CSA should be 90 degrees. Buccal and lingual wall will be converging occlusally. Mesial and distal will be diverged occlusally. Remove all unsupported enamel rods. Enamel rods forming CSA must be full length rods resting on sound dentin or shortened rods resting on sound dentin and covered and supported by the restoration (Noy’s principles) Place cavo-surface margins so that amalgam can be adequately carved and finished.

104

 Features of prepared cavity:     



Outline of the cavity is placed equidistant from the center of the groove. Bucco-lingual width of 1.5 mm through central groove. Bucco-lingual width of 1 mm through other extensions. Pulpal floor is placed 1.5 mm from the enamel surface. Pulpal floor is flat : o Parallel to the occlusal plane of the tooth. o Perpendicular to the long axis of the tooth. Extremities of facial and lingual grooves and walls adjacent to mesial and distal marginal ridges are prepared at 95 degrees to the pulpal floor, this results in a slight flare in these areas.

 Cavity preparation:            

Pencil the defective grooves on the occlusal surface of the tooth. Do not include supplemental grooves. Position the round bur above the central pit so that the bur is perpendicular to the occlusal surface. Enter with the bur to approximately 1.5 mm. Switch to fissure bur (1mm in diameter). Move the bur along the fissures and grooves where the pencil markings are, maintaining your depth of 1.5mm, applying light intermittent pressure. Make sure that the bur is always perpendicular to the occlusal surface. Do not make the cavity wider than the width of the bur. Do not go deeper than indicated (1.5mm). Walls must be parallel or convergent occlusally except at mesial & distal. Eliminate any sharp corners of the cavo-surface outline (reduce the speed of the hp). Remove any debris.

105

2. Class 1 extension cavity:  Indications:    

Deep caries in buccal or/and lingual pits. Deep fissure or groove extended from the occlusal to the lingual or/and buccal surfaces. Fissure crossing the oblique ridge in upper molars. When the remaining oblique ridge in upper molars or transverse ridge in lower premolars is weak  it must be included in the cavity outline to avoid its fracture.

 Resistance form: •

The same as simple class I cavity in addition to: 



Roundation of Axio-pulpal line angle to: o Prevent stress concentration. o Provide bulk to the restoration. The axial wall direction should be parallel to the corresponding external tooth surface, i.e. convex (mesio – distally), in order to: o Prevent pulp exposure. o Provide uniform thickness of the restoration.

 Retention form: •

The same as simple class I cavity in addition to:   

Parallel mesial and distal walls (coefficient of friction). Occlusal lock against lateral displacement. Extension for retention to the opposing surface to provide lateral retention in extensive cavities. Efficient.

 Convenience form: 

The same as simple class I cavity.

106

 Finishing of enamel wall: •

The same as simple class I cavity in addition to:  

The mesial and distal walls of the extension will be completely parallel to each other and to the long axis of the tooth. The gingival floor will be slightly slanting gingivally to be in the same direction as the enamel rods.

Note: class I extension can be: with step or without step (done in practical)

3. Class I buccal pit cavity:  

Buccal pit mostly occur in mandibular molars. It is designed as a simple oval cavity limited to the carious pit and having the following features: 1- Walls of the cavity slight converge buccally to provide retention. 2- Axial wall parallel to the buccal surface of the tooth, convex mesio-distally.

4. Class I lingual pit cavity:  

Lingual pit mostly occurs in maxillary molars. It is designed as a simple round cavity limited to the carious pit and having the following features: 1- Walls of the cavity slight converge lingually to provide retention. 2- Axial wall parallel to the lingual surface of the tooth, convex mesio-distally.

107


Revision: 1- The axio-pulpal line angle in class I facial cavity extension must be rounded, this is referred to as: a- Outline form. b- Resistance form. c- Retention form. d- Convenience form. e- Finishing enamel & dentin wall. 2- For a conservative cavity design the following should be preserved: a- Oblique ridges. b- Transverse ridges. c- Oblique and transverse ridges. d- Pits and fissures crossing the oblique and transverse ridges. 3- The mesial & distal walls in class I cavity preparation for amalgam must diverge occlusally to satisfy: a- Outline form. b- Resistance form. c- Retentive form. d- Convenience form. 4- Typical conservative class I preparation on tooth #26 is: a- Mesial & distal kidney shape. b- Mesial oval (or straight) shape. c- In (H) shape. d- Distal oval (or straight) shape.

108


Student Notes:

109

110

Class V Cavity Preparation for Amalgam
Objectives: 1234567-

Be acquainted of different designs of class V cavity preparation. Know the difference between simple, compound and complex class V cavity. Be able to list and identify different outline forms. Compare between conservative and improper extended cavity. Identify the proper retentive features used in class II cavity for amalgam. Explain of the no Need of convenience form in class V. Be able to identify and differentiate between the proper, correct and incorrect cavity walls and margins and what were the causes of differences. 8- List and know the different orientations of enamel rods of mesial and distal walls. 9- List and explain why we do toilet to the cavity and how to check it. 10- Know, list and explain how gaining access is done using a suitable sized round bur; the direction of cutting is perpendicular to the long axis of the tooth until reaching the dentin. 11- Know, list and explain how lateral extension of the cavity is done using inverted cone bur, proximally. Occlusally and gingivally, the extension should not exceed the high of contour and one mm over the cervical line. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 12- Know, list and explain how finishing of cavity walls and margins are performed using cylindrical fissure bur. The depth of the cavity (axial wall) should be from 0.5-1 mm beyond the DEJ. 13- The directions of the occlusal and gingival walls of the finished cavity should be parallel to the occlusal plane, while the distal and mesial walls should be diverging proximally. The cavosurface angle of the finished cavity should be 90°.

111

Class V Cavity Preparation for Amalgam
Characters of caries:       

Starts as white or chalky line near the center of the gingival third. o (Persisting white chalk = CARIES, NOT INCIDEOUS!) Marked sensitivity. Tendency to spread mesially and distally near the axial line angles of the tooth. Teeth with marked convexity are more susceptible. Less frequent than other types of caries. Usually affects multiple teeth. More frequent among old aged patients and is called “senile caries”.


Outline form: 

   

Usually described as trapezoidal outline, which may be modified by an added box extension to involve proximal caries. o (Class V has 4 point angles + 8 line angles) Occlusal wall: Parallel to the occlusal plane and placed at or just occlusal to the height of contour. Gingival wall: Straight and parallel to the occlusal plane placed just beneath the gingival margin. Proximal walls: Straight and parallel to the direction of the corresponding proximal placed at the line angles of the tooth. Axial wall: 1 mm beyond the DEJ convex mesio-distally and straight occluso-gingivally.

 Resistance form:   

CSA  90°. Bulk of restoration. No need for additional resistance, as the force applied on this area is only the lip and cheek musculature force.

112

 Retention form: 

Grooves in the occluso-axial and gingivo-axial line angles are placed in the expense of the occlusal and gingival walls rather than the axial wall (axio-occlusal and axio-cervical line angles).

 Convenience form: 

No need for convenience in class V cavity preparation.

 Finishing of the enamel wall:   

CSA 90°. Occlusal and gingival walls will be straight and parallel to the occlusal plane. Proximal walls will be slightly diverging outwards to follow the enamel rods.


How to do class V cavity: 1- Access to dentin is gained by a round bur, then the cavity outline is extended using an inverted cone bur to a trapezoidal shape of a width just enough to include the lesion. 2- The walls are flared and finished parallel to the enamel rods with a fissure bur. The floor is made convex in all directions following the pulpal anatomy by an inverted cone. 3- An inverted cone bur is used to place incisal and gingival retentive grooves in dentin at the pulpal line angles and below the DEJ.

113


Revision: 1- To prepare a retentive class V cavity for amalgam restoration: a- Prepare retentive grooves at axio-distal & axio-medial line angles. b- Prepare retentive grooves at axio-pulpal line angle. c- Prepare retentive grooves at axio-occlusal & axio-gingival line angles. d- Prepare convergent walls occlusally & gingivally. e- Prepare divergent walls occlusally & gingivally. 2- In class V cavities for amalgam, the axial wall must be convex mesio-distally so as to: a- Remove all caries. b- Receive equal thickness of amalgam. c- Give means of retention. d- Avoid undermining enamel. e- Provide 95 degrees of cavo-surface margin. 3- In preparing class V cavity for amalgam restoration: a- The gingival wall is straight. b- The mesial and distal are perpendicular. c- The axial wall is convex. d- The occlusal wall is converging facially. 4- In Class 5, the axial wall should be convex: a- Mesio-distally. b- Bucco-lingually. c- Occlusso-gingivally. 5- In class 5 the axial wall is extended: a- 2mm in dentin. b- To the DEJ. c- In enamel. d- Just beyond the DEJ. 6- In class 5 cavity preparation, axial grooves are made to prevent: a- Buccal displacement. b- Gingival displacement.

114


Student Notes:

115

116

Class II Cavity Preparation for Amalgam
Objectives: 123456789-

Be acquainted of different designs of class II cavity preparation. Know the difference between simple, compound and complex class II cavity. Know and identify the different component parts of compound class II cavity. Be able to list and identify different outline forms. Know the proper resistance forms for class II cavity preparations. Compare between conservative and improper extended cavity. Identify the proper retentive features used in class II cavity for amalgam. Explain of the Need of convenience form in class II. Be able to identify and differentiate between the proper, correct and incorrect cavity walls and margins and what were the causes of differences between ( the uniform, straight and reverse curve ) buccal wall extension. 10- List and know the different orientations of enamel rods, and what consequences can develop for leaving undermined enamel. 11- List and explain why we do toilet to the cavity and how to check it. 12- Know, list and explain how gaining access is done using a suitable sized round bur; the direction of cutting is parallel to the long axis of the tooth until reaching the dentin. The cutting is done through the weakest portion of the tooth, i.e. central or proximal triangular fossa. 13- Know, list and explain how lateral extension of the cavity to include all pits and fissures is done using inverted cone bur and the proximal cavity will be created buccally, lingually and gingivally. The extension should not exceed the 1/3 inter-cuspal distance for isthmus portion. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 14- Know, list and explain how finishing of cavity walls and margins is performed using cylindrical fissure bur. The facio-lingual dimension of the cavity should be ¼-1/3 the inter-cuspal distance, while the depth of the cavity should be from 0.5-1 mm beyond the DEJ. And understand the different widths of gingival floor for premolar and molar. 15- The directions of the facial walls for lower posterior should be converge and lingual wall should be straight while the lingual cavity wall should be converging occlusally for upper posterior teeth and the facial walls is straight. Axial wall should be convex facio-lingually. The cavosurface angle of the finished cavity should be 90°.

117

Class II Cavity Preparation for Amalgam
Definition: It is a smooth surface cavity that occurs in the proximal surface of the posterior teeth.


Design for class II cavity preparation: 1- Class II simple cavity (adjacent tooth is missing or there is a space between adjacent tooth). 2- Class II compound or complex cavity with proximal step. 3- Class II compound or complex cavity without proximal step (3rd molars distal surface).


Characters of caries class II cavity preparation:   

  

Difficult to detect until it reaches a considerable size. Bite wing radiographic film is necessary for correct diagnosis. Spreads in enamel and dentin in conical pattern. - In enamel the cone base is at the surface and pointed towards the DEJ. - In dentin  the cone base is at the DEJ and pointed towards the pulp. Tends to spread occlusally along the DEJ leading to early undermining of the proximal marginal ridge. Tends to extend bucco-lingually towards the axial line angles and also gingivally. Tendency of caries recurrence at the bucco-gingival and lingo-gingival line angles of the cavity.


Class II compound or complex cavity with proximal step: It is composed of 3 portions: 1. Occlusal portion. 2. Isthmus portion. 3. Proximal portion.

118

A) Outline form: 1- Occlusal portion: Same as occlusal class I cavity. 2- Isthmus portion: -

Definition: The narrowest connection between the occlusal and proximal portions of class II compound or complex cavity.

-

The outline of the isthmus portion should be extended to: a- Involve all the carries in enamel and dentin. b- Place the cavity margins in an area self-cleansable with freeingof the proximal contact area.

-

According to:  The occlusal anatomy of the tooth.  Position and size of the proximal contact area.  Width of the embrasure.

-

The isthmus outline form may follow one of the following Ingrham’s lines:  Straight: in case of small contact area.  Uniform: in case of normal sized contact area.  Reverse curve: in case of broad or wide contact area.  The width of the cavity at isthmus should be narrow bucco lingually as much as possible  about ¼ of the inter-cuspal distance.

119

3- proximal portion: 

  

  

Should be extended enough to ensure: o Involvement of all carious enamel and dentin. o Freeing the proximal surface out of contact lingually, buccally and gingivally. o Placing the cavity margins in the embrasures to be in an area self-cleansable. The buccal wall is mid-way between the contact area and the bucco-axial line angle in a direction parallel to the corresponding buccal surface of the tooth. The lingual wall is mid-way between the contact area and the lingo-axial line angle in a direction parallel to the corresponding lingual surface of the tooth. The gingival floor is 0.25 – 0.5 mm above the gingival crest of the free gingival margin and in a direction parallel to the pulpal floor and occlusal plane of the tooth i.e. being in an area less susceptible. The axial wall is about 1.5-2 mm away from the DEJ to provide enough bulk of the restoration. The axial wall should be in a direction parallel to the external proximal tooth surface. It will be either straight or convex to provide: o Enough uniform bulk of the restoration. o Protection of the pulp against traumatic exposure.

120

B) Resistance form: 1- Occlusal portion: Same as class I cavity. 2- Isthmus portion:   



Minimal width of the cavity bucco-lingually is about ¼ of the inter-cuspal distance. This will provide a decrease in the surface area of the restoration subjected to the occlusal stresses. Roundation, beveling or saucerization of the axio-pulpal line angle, to provide: o Removal of the sharp axio-pulpal line angles that act as a stress concentration area. o Increased bulk of the restoration at the isthmus area.

Reverse curve, in case of wide proximal contact area, will provide: o Maximum conservation of the sound tooth structure during freeing of the contact. o Removal of all undermined enamel. o Correct CSA  90°.

3- Proximal portion:      

Reverse curve approach  in the buccal wall of upper premolars to remove all the undermined enamel. CSA 90°. Gingival floor  smooth, flat and parallel to the pulpal floor and the occlusal plane. Axial wall parallel to the external proximal tooth surface and at 1.5 -2 mm away from the DEJ, this will provide uniform bulk of the restoration. Buccal and lingual walls parallel to the direction of the corresponding surfaces. The proximal portion is in box form. 121

C) Retention form: •

Axial retention: 1234-

•

Mechanical under cuts by preparing the cavity walls slightly converging occlusally. The inverted truncated cone shape of the proximal portion. Proximal axial grooves. Pin retention in extensive cavities placed in the gingival floor.

Lateral retention: 1- Proximal dovetail:  In premolars, considered as extension for retention.  In molars, considered as extension for prevention that provides retention also. 2- Occlusal lock. 3- Proximal axial grooves. 4- Pin retention in extensive cavities. -

Proximal axial grooves:  Cut in the axio-buccal and axio-lingual line angles, in the expense of buccal and lingual walls rather than the axial wall to avoid pulp exposure.  Extended from the gingival floor in occlusal direction up to the level of the pulpal floor.  These grooves are: o Wider internally than externally. o Wider gingivally than occlusally. o Prepared using small round bur or small tapered fissure bur.

-

Convenience form:  Cutting an occlusal cavity is considered as a convenience form as it provides accessibility to the proximal portion.  Accentuation of cavity walls and margins.  Roundation of line angles.  The axial wall should be parallel to the tooth long axis in occluso-gingival direction to allow instrumentation up to the depth of the proximal portion.  Selection of suitable sized instruments.

122

D) Finishing of enamel wall: 1- Occlusal portion: Same as class I cavity. 2- Isthmus portion: 

following Ingrham’s lines will provide: a- Enamel wall in the direction of enamel rods with CSA = 90°. b- Enamel wall free from any loose, undermined or friable enamel rods.

3- Proximal portion:   



 

The buccal and lingual walls are flared slightly outward to get CSA = 90°. The gingival floor is slanted slightly gingivally to get CSA = 90°. Reverse curve approach: o In the buccal wall of the proximal portion of the upper premolars, after performing reverse curve outline of the isthmus portion, the enamel of the buccal wall will be undermined. Beveling of the enamel of this buccal wall will provide: a- Removal of all undermined enamel. b- CSA = 90°. Bin-angle chisel or enamel hatchet are the instruments used for this purpose. Gingival marginal trimmer to trim the gingival wall.


Clinical considerations: 1- It is preferable to complete the proximal outline before breaking the marginal ridge and the proximal enamel plate. This will provide: a- A guide to proximal design. b- Protection of the proximal surface of the adjacent tooth from rotary instrument. c- Save time and effort. d- Reduce heat generation as cutting in enamel produces much more heat generation.

123

2- The reverse curve outline will be followed in the buccal wall more than the lingual as the contact area is much more shifted buccally, the reverse curve may provide: a- Enamel wall in the direction of the enamel rods. b- CSA = 90°. c- Freeing of the contact area with maximum conservation of the tooth structure. d- Increased bulk of the restoration which may provide lateral retention. 3- In large cavities, whenever a cusp is undermined or becomes weak it must be reduced and covered with a minimum of 2mm thickness of the restoration and this is called cusp tipping or cusp reduction. This is common in occluso-distal cavities in the lower first molars where the distal cusp is easily weakened.

124


Revision: 1- In order to prevent isthmus fracture of dental amalgam restorations, the following line angle/s should be rounded: a- Axio-pulpal line angles. b- Axio-gingival line angles. c- Axio-pulpal & Axio-gingival line angles. d- Axio-mesial line angles. 2- A patient has caries lesion occurred only in the mesial surface of his tooth #27, while his #26 was extracted. The prepared class II cavity preparation on this tooth is supposed to be: a- Simple class II cavity preparation. b- Compound class II cavity preparation. c- Compound class II cavity preparation with facial extension. d- Compound class II cavity preparation with lingual extension. 3- In class II cavity, axial wall should be convex: a- Mesio-distally. b- Bucco-lingually. c- Gingivo-pulpally. d- Occluso-gingivally. e- Mesio-buccally. 4- To achieve a proper resistance form, the gingival floor of class II cavities for amalgam should be prepared: a- Following the direction of enamel rods. b- Parallel to the pulpal floor. c- With flat dentinal floor and gingivally trimmed enamel floor. d- With flat enamel floor and trimmed dentinal floor. 5- When restoring compound class II cavities, dental amalgam should be placed first in the: a- Deepest areas in the proximal part. b- Occlusal part. c- Lateral walls. d- Axial walls.

125

6- Optimum uniform depth of pulpal floor in class II cavity for amalgam is necessary to prevent: a- Undermining of enamel. b- Fracture of the tooth structure. c- Fracture of the amalgam restoration. d- Displacement of the amalgam restoration. e- Pulpal involvement. 7- In class II cavity preparation for amalgam, axial grooves are made to prevent: a- Gingival displacement. b- Gingiva pulpal displacement. c- Lateral displacement. 8- in class II cavity preparation for amalgam, the axial wall extends: a- Beyond DEJ. b- 2 mm in dentin. c- In enamel. d- To DEJ. 9- Functions of the reverse curve include: a- Finishing CSA at 90°. b- Removing undermined enamel. c- Preserving tooth structure. d- All of the above.

126


Student Notes:

127

128

Chapter 6: Direct Restorative Materials

129

Amalgam
Objectives:       

Identify dental amalgam and its basic composition. Recognize different types of dental amalgam. Be on familiar terms with the characteristics of dental amalgam. Recognize the indications for dental amalgam. Understand the basic setting reaction and the process of amalgamation. Be acquainted with the procedural steps of dental amalgam manipulation. Be able to improve the clinical performance of amalgam restoration.

130

AMALGAM
Definitions:  Amalgam: an alloy of mercury and one or more other metals.  Alloy: mixture of metals.  Dental Amalgam: mixing of mercury with solid particles of an amalgam alloy powder (powder of Silver, Tin, Copper, Zinc, Palladium, Indium and Selenium.


Basic composition: 1- Powder (amalgam alloy): Silver, Tin & Copper. 2- Liquid mercury (Hg). 3- Additives: zinc, indium & palladium.

1. Alloy power composition: 1- Silver (Ag): 67-74% by weight.  Increases: o Strength. o S. expansion. o Resistance to tarnish and corrosion.  Decreases: o Creep. o Setting time. 2- Tin (Sn): 24-28%by weight.  Facilitates the reaction because of its affinity to Hg.  Increases: o Setting time. o Corrosion.  Decreases: o Strength. 131

o S.expansion. 3- Copper (Cu): 0-30% by weight.  Increases: o Strength. o Hardness.  Decreases: o Corrosion. o Creep.

2. Liquid Mercury (Hg):  

The only metal which is liquid at room temperature. Used to liquefy and react with dental amalgam alloy producing a plastic mix, which remains workable at room and body temperature for a reasonable period of time.

3. Additives: 1- Zinc (Zn): 0- 2%  Scavenger of oxides during manufacturing.  Provides better clinical performance.  Less marginal breakdown.  If contaminated with moisture during condensation: o H2O + Zn = ZnO + H2 o Patient suffers from pain. o Restoration deterioration. o Roughness of the surface due to ditches and blisters. 2- Indium ( In) : 0-10%  Increases: o Affinity to Hg. o Strength.  Decrease: o Surface tension. o Amount of mercury necessary. o Emitted mercury vapor. o Creep.

132

3- palladium (Pd): 0.5 %  Increases luster.  Decreases corrosion. INCREASE SILVER, COPPER, INDIUM

STRENGTH CREEP SETTING TIME S. EXPANSION TARNISH CORROSION HARDNESS

TIN SILVER TIN COPPER

SILVER COPPER TIN

INCREASE STRENGTH, S.EXPANSION STRENGTH, HARDNESS SETTING TIME, CORROSION

INDIUM

STRENGTH, AFFINITY TO Hg,

PALLADIUM

LUSTER

DECREASE TIN SILVER, COPPER, INDIUM SILVER TIN SILVER COPPER, PALLADIUM

DECREASE CREEP, SETTING TIME, TARNISH CREEP, CORROSION STRENGTH, S.EXPANSION CREEP, SURFACE TENSION, AMOUNT OF MERCURY, EMITTED MERCURY VAPOR CORROSION


Amalgamation reaction: 1- Mercury dissolves the surface of alloy particles 2- Metals in particle combined with mercury in phases which precipitate out in the form of new reaction product (γ1 and γ2 phases) [the matrix]. 

The matrix holds the remaining un-reacted particles together as a coherent mass. Ag3Sn + Hg Ag2Hg3 + Sn8Hg + Ag3Sn (γ phase)  (γ1 phase) + (γ2 phase) + (unreacted γ phase)

133

 Symbols of phases: 123456789-

Ɣ = Ag3Sn Ɣ1 = Ag2Hg3 Ɣ2 = Sn8Hg ε = Cu3Sn η = Cu6Sn5 Different composition = AgCu A silver-mercury containing filler particles of silver-tin. Filler : Ag3Sn called gamma Matrix:  Ag2Hg3 called gamma 1.  Cement.  Sn8Hg called gamma 2.


Copper Content: 1- Low copper alloys: (conventional) 4-6 % Cu 2- High copper alloys: (modern) 12- 30 % Cu at expense of Ag  Higher strength, corrosion resistance.  Lower creep.


Zinc containing:  

Zinc containing: containing Zn > 0.01%. Zinc free: containing Zn =< 0.01%.


Particle Shape:  Lathe cut:   

Low Cu. High Cu. Irregular particles. 134

 Spherical:   

Low Cu. High Cu. Spheres particles.

 Admixed:   

Admixture of lathe cut and spherical particles. High Cu. Disperse alloy.


Particle size:   

Regular. Fine. Micro-fine. o A powder containing tiny particles requires less amount of mercury to form an acceptable amalgam. o A small to average particle size  a more rapid hardening and a greater early strength. o Particle size distribution can affect the character of the finished surface. o Large particles may be pulled out during carving  a rough surface  corrosion.


Physical properties:     

High Thermal conductivity (and thermal diffusivity). Electrical conductivity. Coefficient of thermal expansion (the higher the coefficient, the greater the dimensional change of the material following thermal fluctuation). Radio opacity (radio opaque). Color.

135


Dimensional change:      

Net contraction of 20 µm after setting. Contraction leaves marginal gap. How to improve initial adaptation? o Apply varnish (which can be applied on both dentin and enamel). How to improve late adaptation? o Corrosion products of the amalgam. Increase condensation  higher adaptation and less expansion. Spherical alloy show more contraction.


Mechanical properties:  Strength:   

High compressive strength. Low tensile strength. How to improve the strength of the amalgam? o Proper cavity design. o Proper condensation. o Elimination of excess mercury.

 Creep:  

Clinically: margins over extended from the cavity which lead to the restoration breakage. Creep leads to: 1- Marginal breakdown. 2- Gingival overhangs: (by improper placement or creep) leads to food accumulation  caries. 3- Alteration of form & contours.

 Tarnish: Change in the color of the restoration (esthetic).

136

 Corrosion:   



Chemical corrosion: on the surface. Electrochemical corrosion: change in the chemistry of amalgam, seals the margins. Crevice corrosion: o Due to different oxygen concentration inside the same restoration. o Between highly polished and finished amalgam and poorly polished and finished amalgam. Stress cell corrosion: between areas subjected to occlusal forces and another not subjected to forces.


Advantages of amalgam: 1- Superior adaptability to cavity walls and margins: (V. imp)  

Provides good seal. Prevent marginal leakage after a period of time in the mouth.

2- High compressive strength: 

With sufficient thickness can sustain occ. Forces without fracture.

3- Low coefficient of thermal expansion: 

Compared to other materials: o Amalgam  25 ×10-6. o Tooth  11.5 × 10-6.

4- Indestructible in oral fluids: 

High copper with high creep resistance can maintain proper anatomy, proximal contact form and contour.

137


Disadvantages of amalgam: 1234567-

Brittleness: low tensile strength. Poor esthetic (metallic color). Tendency for tarnish and corrosion. Thermal conductivity. Creep. Does not help retain weakened tooth structure. Concerns about mercury toxicity.


Applications:     

Direct, permanent, posterior restoration. Small and medium size cavities of class I, II and VI. Large foundation restoration. Cores for crown or fixed partial denture restoration. Provisional restoration.


Quality of dental amalgam: 

Controlled by the dentist: 1- Alloy selection. 2- Mercury alloy ratio. 3- Trituration procedures.


Selection of alloy: High copper is always better.

 Particle size: Finer always better.

 Particle shape:

138

Spherical requires less Hg because it has less surface area. • Lathe cut: Higher resistance to condensation. •

•

Spherical: -

Advantages:  Hardens rapidly.  Needs lighter condensation.  Smoother polish.  Higher early strength.

-

Disadvantages:  Difficult to achieve tight contacts.  Higher tendency for overhangs.

-

Indication:  Pulp capping.  Pin retained restoration.  Multiple retentive means.

Admixed: -

Advantages:  Easy to achieve tight contacts.  Ease of attaining contours and forms.  Good polish.

-

Disadvantages:  Hardens slowly.  Lower early strength.

-

Indication:  Large restoration to build up proper contour and contacts.  Cases which require recontouring.  Zinc + water = delayed excessive expansion  pulpal pain in 3-7 days.

139

o Zinc free is used in cases with difficult moisture control (e.g. children) because zinc + moist will cause excessive delayed expansion.


Capsules: 

  

Contains (in separate compartments) pre-proportioned: o Powdered amalgam alloy. o Liquid mercury. Some are manually activated, others are self-activated. Pestle usually included. The most convenient as it is: o Properly dispensed and proportioned. o More hygienic as it is well sealed and the operator will not subjected to Hg vapors. o Lesser manipulation procedures.


Proportions of alloy to Hg: 

Several smaller mixes would be made at spread out times so the consistency of the mixed amalgam remains reasonably constant during the preparation of the restoration.

 Aims: 1- Select the proper amount of mix required to fill the cavity depending on:  Size of the cavity, which must be slightly overfilled.  The amount which could be condensed in 3-5 minutes. 2- To select the proper amount of Hg required to wet every alloy particle without affecting the final properties of amalgam restoration.

 Excessive Hg:    

Excessive expansion. Drastic loss of strength. Increased creep. Increased tarnish and corrosion.

140

 Insufficient Hg:     

Non coherent mix (friable). Weak. Corrodible. Full of voids. Proportioning.


Trituration: (mixing of amalgam) Manually or mechanically by amalgamator for capsules

 Aims:  



Good trituration: coherent. Over trituration (hot mix): o Faster setting. o Higher early strength. o Better surface. o Slightly higher contraction. o Adheres to the mortar. Under trituration (less mix time): o Friable. o Non-coherent. o Dull. o Non-homogenous. o Weak. o Corrodible. o Increases setting time.


Squeezing and mulling:  Aims: 

To reduce the amount of excess hg (squeezing) 141



To increase the homogenicity and plasticity of the mix ( mulling )

 Technique: 1- Squeezing:   

Utilized when high hg is present. Squeezing of amalgam mix in a piece of gauze. Sufficient hg must be left to ensure cohesion of the mix. SQUEEZING ONLY WITH AMALGAM WITH EXCESS MERCURY

2- Mulling:  

Rubbing of the mix against a piece of rubber Improve plasticity


condensation of amalgam: Procedure of packing of the freshly triturated amalgam into the prepared cavity through homogenous manner.

 Aims:     

Improving adaptation of amalgam to cavity walls and margins. Improving adaptation of successive increments of amalgam (no layering). Elimination of voids and excess Hg. Increasing density of the amalgam through packing of the particles. Over filling of the cavity in order to: o Allow proper carving. o Get the Hg rich layer at the surface that will be removed with carving.

142


Pre-carving burnishing:  

Using large sized burnishers with heavy pressure directed from the tooth to the restoration. It provides the followings: 1- Increased adaptation of amalgam to cavity walls and margins. 2- During this, some frictional heat is generated which helps the excess Hg to be attracted to the surface and easily removed with carving. 3- More cohesive amalgam. 4- Establishment of initial anatomy to be continued by carving.


Carving: 1- Rebuilding the tooth to its normal intact state. 2- Proper tool in proper direction and angulations.

Never carve from restoration to tooth structure.


Post-carving burnishing: 

Small sized burnishers with gentle strokes are used to smoothen the amalgam surface. 143



Checking of occlusion right after putting the amalgam polishing after 24 hours.

144


Revision: 1- Cavo-surface angle of amalgam cavities should be made 90 degrees because amalgam has: a- Low compressive strength. b- Low tensile strength. c- Tendency to flow. d- Tendency to creep. 2- Hot mix indicates: a- Under trituration. b- Over trituration. c- Excess mercury. d- Proper trituration. 3- The adaptability of amalgam restoration to cavity margins improves overtime with: a- Corrosion products. b- Creep. c- Proper application of varnish & base. d- Flow. 4- Post-carving burnishing of amalgam should be done to: a- Improve adaptation to cavity margins. b- Increase density of amalgam. c- Eliminate excess mercury. d- Smoothen the restoration. 5- An 18-year old patient came to the clinic with a deep class I carious lesion. Pulp capping was required after caries excavation. Which one of the following is the best to be used: a- High copper lathe-cut amalgam. b- High copper spherical amalgam. c- High copper admixed amalgam. d- Low copper spherical amalgam.

145

6- Varnish should be used to improve the initial adaptation of amalgam. However, amalgam adaptation improves with time due to creep. a- First statement is TRUE, the second is FALSE. b- First statement is FALSE, the second is TRUE. c- Both statements are TRUE. d- Both statements are FALSE. 7- Checking of amalgam restoration for proper occlusion should be done: a- Shortly after carving. b- After one hour of displacement. c- After 24 hours. d- After 48 hours. 8- After 4 days of placing Zn-containing amalgam in a sub-gingivally extended class II cavity, the patient complained of pulpal pain. This is may be due to: a- Premature contact. b- Delayed expansion. c- Galvanism. d- Creep. 9- Sub-margin or ditching of the amalgam restoration can occur due to: a- Incremental packing of amalgam. b- Lack of post-carving burnishing. c- Carving in the direction from the restoration towards the tooth. d- Corrosion. 10- In a large amalgam restoration that requires proper contouring, which of the following should be used: a- Conventional spherical amalgam. b- High copper admix amalgam. c- High copper spherical amalgam. d- Conventional lathe cut amalgam.

146

11- Admixed amalgam has the properties of fast hardening and attaining higher early strength. On the other hand, spherical amalgam has properties of slow hardening and lower early strength. a- First statement is TRUE, the second is FALSE. b- First statement is FALSE, the second is TRUE. c- Both statements are TRUE. d- Both statements are FALSE. 12- In order to reduce setting time without greatly affecting the amalgam properties, it is advisable to: a- Increase the trituration time. b- Decrease the trituration time. c- Increase the Hg/powder ration. d- Decrease the Hg/powder ratio. 13- Delay in condensation of amalgam: a- Makes it impossible to remove Hg effectively during condensation. b- Allows proper carving of the amalgam. c- Provides stronger amalgam restoration. d- Decreases the adverse effects of Hg. 14- Admixed verses spherical amalgam: a- Requires less Hg/powder ratio. b- Is difficult to achieve tight contact with. c- Has a smoother surface. d- Requires greater condensation force. 15- Placement of a large amalgam restoration is best achieved by: a- Several small mixes to be triturated at spread out times and condensed in layers. b- Several small mixes to be triturated at the same time and condensed in layers. c- One large mix condensed in layers. d- One large mix condensed in a bulk technique. 16- Over filling of the cavity during condensation of amalgam is indicated: a- To increase amalgam strength. b- To allow proper carving. c- Only in high copper amalgam alloys. d- Only in low copper amalgam alloys.

147

17- Excessive delayed expansion occurs into zinc containing amalgam due to: a- Contamination with saliva during insertion. b- Contamination with saliva during carving c- Contamination with saliva during checking of occlusion. d- Contamination with humidity during storage. 18- An overextended cavity with many retentive means prepared to be restored with amalgam, which of the following is the best to be selected: a- High copper lathe-cut amalgam. b- Low copper spherical amalgam. c- High copper admixed amalgam. d- High copper spherical amalgam. 19- In amalgam restoration, the angle between the cavity and the tooth surface is: a- 90°. b- Obtuse. c- Acute. 20- Depth of amalgam cavities should be extended just below the DEJ in order to: a- Remove all under mind enamel. b- Give bulk to the restoration. c- Place the restoration in dentin. d- Get benefit from the gripping action of dentin. 21- Conventional and modern amalgam are classified according to: a- Copper content

148


Student Notes:

149

150

Finishing & Polishing of Amalgam Restorations
Objectives: By the end of this lecture the student must be able to: 1- Define & differentiate between finishing and polishing concepts of amalgam restorations. 2- Enumerate and describe Clinical significance of finishing & polishing of amalgam restorations. 3- Identify & compare between the different rotary instruments used for finishing & polishing of amalgam restorations. 4- Describe the different techniques used for proper finishing & polishing of amalgam restorations. 5- Describe precautions & control measures should be taken finishing & polishing of amalgam restorations. 6- Summarize & list the standard clinical steps (sequences) used during finishing & polishing of amalgam restorations

151

Finishing & Polishing of Amalgam Restorations
Burnishing: a. It is the rubbing of the amalgam surface with a blunt instrument immediately after carving to smooth the surface. b. It improves margin adaptation and facilitate later finishing and polishing. c. Types: Pre-carving & Post-carving burnishing.  

Finishing amalgam restorations involves removing marginal irregularities, defining anatomical contours, and smoothing the surface roughness of the restoration. Polishing is performed to obtain a smooth, shiny luster on the surface of the amalgam.


Clinical Significance of Polishing: 1. It improves stress response of the restoration by elimination of surface roughness that causes stress-concentration. 2. It increases corrosion resistance by increasing surface homogeneity and elimination of surface dissimilarities that create galvanic cells. 3. It improves biocompatibility with soft tissues through provision of smooth surfaces that inhibit plaque accumulation and preclude mechanical irritation. 4. It inhibits colonization of bacterial plaque and decreases vulnerability to caries recurrence. 5. It confers better esthetics and patient’s acceptance and thus, encourage better home-care.    

Tarnish is a discoloration on the surface of the amalgam. Corrosion is a destructive attack on both the surface and subsurface of the restoration. A minimum of 24 hours must elapse between insertion of the restoration and finishing and polishing. An amalgam restoration is not considered complete until it is polished.


Rotary Instruments Used for Amalgam F & P:  

The most commonly used rotary instruments are abrasive stone, disks and finishing burs. The choice of abrasive stones, disks, and burs is dependent upon the size of the restoration, the adaptability to the tooth surface, and the amount of amalgam to be removed.

152


Finishing:  

Use small green & white stones for gross removal of excess amalgam and for dressing down amalgam margins to remove all marginal excesses, or "flashs“. Use finishing burs to refine the anatomy and contours of the occlusal surface and marginal ridge areas.


Green Stones:   

Available as tapered points pear shape, round or a variety of other shapes. They are fast cutting and produce a moderately rough surface. Since the green stone is harder than enamel, care must be taken not to scratch the tooth surface.


Finishing Disks:       

Disks are used primarily on the proximal, buccal, or lingual surfaces. Available in a variety of sizes and grits. Use of a medium grit disk is always followed by the application of a finer grit disk which cuts less. Disks of various grits (e.g. Soflex) may be used to smooth proximal areas and refine proximal margins. These disks should be kept in constant motion to avoid "ditching" (damage of the newly placed restoration or existing tooth structure). Types: Garnet, Sandpaper, Cuttle. Fineness: Coarse, medium, fine, Ultrafine.


Interproximal Finishing Strips:   

Coarse, medium, fine, super-fine. Insert and use below contact area to maintain proximal contact. Wedge if needed.

153


Finishing Burs:  

Differ from cutting burs in number of blades ( more blades ) Finishing burs should be operated in the burnishing direction rather than cutting direction.


Polishing Agents:  

Pumice and tin oxide are two commonly used polishing agents. Other polishing agents are available in the form of abrasive-impregnated rubber points and cups. They are to be used in the following order: Brownies, Greenies, and Super Greenies.

Note:  Brownies (coarse) and greenies (fine) are rubber abrasives points that can be used during the finishing procedure.  If used, they should follow the use of finishing burs.  Be cautious during manipulation of these rubber points.


Brownie®, Greenie®, Supergreenie® Rubber polishers: 

These popular silicone polishers are impregnated with high-quality polishing ingredients for fast, brilliant polishing on precious metals and amalgam.


Polishing:   

During polishing, use a wet slurry of polishing abrasives (pumice). The only abrasive recommended for dry polishing is amalgloss (or tin oxide). Rotate rotary instruments parallel to amalgam/tooth margins or from tooth structure to amalgam. Polishing abrasives should be used as needed in the following order: coarse pumice, fine pumice, tin oxide (amalgloss).


To Minimize Heat Production During Amalgam Polishing:    

Use light, intermittent pressure with rotary instruments. Use slow to moderate speed. Use abrasive agents that are wet rather than dry (e.g. pumice slurry). Use compressed air directed at the amalgam surface during polishing. 154


Important Hints:            

Check the Marginal Integrity of the restoration before F & P procedure. Flash = amalgam excess. Submargin = amalgam deficiency. “Ditching” = carving error. Voids / Pits = condensation error. Use appropriate shape burs in a low speed HP. Use rotary burs and points perpendicular to margins, or rotation from restoration toward margins. Mounted green (coarse) and white (medium) stones. Brownie (medium - fine), and greenie (fine) points and cups. Pumice (medium) while Tin oxide (fine). Moisten pumice with water in brush cup or rubber cup. Moisten tin oxide with alcohol in rubber cups.

155


Amalgam Polishing Procedures: This section will introduce one technique for polishing amalgam restorations. Each operator has her/his own favorite equipment and technique for most effectively polishing amalgam restorations. A step-by-step approach is offered so that the student may first become competent with this method, and may then develop her/his own particular technique through practice activities. The following armamentarium is needed for this procedure.

 Step 1: Evaluate Restoration to be Polished  Step 2: Check Occlusion of Restoration  Step 3: Isolate  Step 4: Smooth Occlusal Cavo-surface Margins The primary objective of amalgam polishing is to achieve smooth, flush cavo-surface margins which will resist plaque accumulation and contribute to the health of the tooth and surrounding soft tissues. The margins can be smoothed easily by using a round bur. Choose #4 or #6 round finishing bur—whichever will best fit the area you are working on. Place the side of the bur against both amalgam and tooth surface. Use medium speed and light pressure to prevent excessive reduction of the amalgam or cutting away tooth structure. Move the bur along all cavo-surface margins. This procedure is not designed to reshape, rather it is to assure that the blend of tooth structure to amalgam is perfect. Run the tip of an explorer back and forth across the margins to ascertain if they are smooth and flush.

 Step 5: Smooth Occlusal Surface Further smoothing of the amalgam surface is accomplished with the use of a large round finishing bur. Again, choose #4 or #6, whichever best fits the area you are working on. This step is often times completed in conjunction with step 7. If marginal discrepancies are minimal, it is possible to smooth the broad occlusal surfaces and marginal ridges while working on the cavosurface margins. Smooth the entire occlusal surface and marginal ridges, using the side of the finishing bur. Use light pressure and moderate speed as you move the bur back and forth across all surfaces.

156

 Step 6: Smooth Proximal Cavo-surface Margins and Surface Check the restoration frequently with the explorer to evaluate the integrity of the margins and to determine the smoothness/roughness of the polished surface.

 Step 7: Smooth Facial and Lingual Surfaces Smooth convex facial and lingual surfaces with finishing desks. Adapt the edge of the disk to the margin of the restoration and, using a light sweeping stroke, move the disk toward the occlusal surface of the tooth. Smooth the amalgam with a less abrasive (fine) disk. When a concave area is involved, such as near the buccal or lingual grooves, use a finishing bur to smooth the area.

 Step 8: Polishing the Restoration The polishing phase consists of first removing the very light scratches remaining after use of the finishing burs. It is achieved by using progressively finer abrasive agents and can be accomplished by the use of a couple of different methods—or a combination of the two methods:

A. Pumice and Tin Oxide: Flour of pumice is mixed with water to form slurry. It is applied to all surfaces with a rubber cup. Use fairly light pressure and sweeping strokes, adapting the cup to marginal ridges and as far inter-proximally as possible. Replenish the moist pumice often since the pumice should do the polishing—not the rubber cup. Rinse and evacuate all pumice from the area. The amalgam should have a smooth, satin finish (dull luster). If deep scratches and irregularities are present, return to the appropriate finishing bur. Tin oxide may be used in a wet slurry or dry. It is applied in the same manner as the pumice. If you do not change rubber cups after applying the pumice, be certain to wash the pumice out of the cup to remove the coarser pumice particles before applying the tin oxide. Use a light buffing motion and a slightly higher speed with the handpiece to create a shiny, mirror-like finish.

157

B. Abrasive Points: Adapt the Brownie abrasive point into the concavities of the occlusal surface and rest the side of the cavo-surface margin. Using light pressure and low speed move the point over all areas of the amalgam that is accessible. As with pumice, the surface should be a dull luster after use of the brownie. Using the same technique as described for the Brownie, use the Greenie. The surface will become much shinier, but will not yet have a mirror-like finish. Repeat above steps using the Super-greenie. It is the least abrasive of the three points (equivalent to tin oxide), and it use should result in a mirror-like shine on the surface of the amalgam.

 Step 9: Rinse and Evacuate All Debris Rinse and evacuate all debris completely. Floss the interproximal surface with clean dental floss just as though you were removing plaque from the area to help remove any remaining abrasive from the interproximal space.

 Step 10: Evaluate Polished Amalgam Evaluate all margins and surfaces of the restoration with the tip of explorer

 Step 11: Recheck Occlusion Remove the rubber dam or cotton rolls and recheck the occlusion with articulating paper.


Standard Summary:          

Check the occlusion Examine the margins Finish the small, round FB to …. Use small bear shape FB to …. Use large bear shape FB to …. Examine the restoration with …. To ….. Begin polishing procedure with pumice slurry and black PC Rinse thoroughly Final polishing with clean RC and tin oxide powder Rinse thoroughly, Re-examine & Final occlusion check

158

159


Revision: 1- To minimize heat production during Amalgam polishing: a- Do not use big size rubber points b- Avoid using latch-type low speed finishing burs. c- Use continuous air coolant with proper high suction. d- Use wet abrasive agents at low speed with light, intermittent pressure. 2- Mulling of the dental amalgam mix can be done by rubbing of the mix against a piece of: a- Cotton. b- Rubber. c- Gauze. d- Cloth. 3- The operators choice for stones, disks or burs for finishing of amalgam restoration is dependent upon: a- Patient preference & cooperation. b- Time elapsed after insertion of amalgam restoration. c- Number of restorations need to be finished & polished per visit. d- Size, location and adaptation of amalgam restoration. 4- Final polishing of amalgam restoration is better to be done with: a- A clean rubber cup & tin oxide powder. b- New big size finishing burs. c- Soflix disks. d- Suitable shape white stones 5- To minimize heat production during Amalgam polishing: a- Do not use big size rubber points b- Avoid using latch-type low speed finishing burs. c- Use continuous air coolant with proper high suction. d- Use wet abrasive agents at low speed with light, intermittent pressure.

160


Student Notes:

161

162

Amalgam Safety & Mercury Hazards
Objectives: By the end of this lecture the student must be able to: 1- Describe the physical properties, forms & uses of mercury. 2- Describe symptoms of mercury toxicity and recognize scientific facts regarding this issue. 3- Identify the different sources of mercury exposure in dental office. 4- List different factors affecting mercury leakage of amalgam capsules and describe a simple method to check for this leakage. 5- Identify & interpret on historical issues of amalgam wars due to mercury content. 6- Identify the Threshold Limit Value ( TLV) for mercury vapor exposure and describe different methods used for of detection of this vapor at dental operatory & personnel. 7- List and criticize claims of anti-amalgamists regarding mercury toxicity of amalgam restorations. 8- Identify the recommended hygienic protocols for management & disposal of amalgam waste. 9- List different available mercury-free direct metallic restorations and describe the Ethical & Scientific issues regarding amalgam replacement with esthetic non-metallic restorations. 10- List & recognize the updated ADA Dental Mercury Hygiene Recommendations.

163

Amalgam Safety & Mercury Hazards
Mercury:    

One of the few metals that is liquid at room temperature. Used in medicinal preparations, for more than 2000 years, such as Diuretics, laxatives, skin preparations. Used in over 60 industrial applications: Chlorine production, insecticides, neon lights, paint, etc… Present in the environment and it is taken into the body in one form or another via water, air and food on daily basis.


Mercury Uses:        

Thermometers. Electric Switches. Fluorescent Lamps. Batteries. Insecticides. Rat poisons. Disinfectants. Dental Amalgam.


Physical Properties of Mercury:    

Melting Point = -38°C Boiling Point = 356°C Density = 13.5 gm/ml Low heat of vaporization allows oxide-free metallic Hg to evaporate easily at room temperature.

164


Forms of Mercury:      

Metallic - Hg - Stable/Unreactive Ionic - Hg+ - Reactive/Not a HazMat Salts - HgCl - Mercuric Chloride Compounds - Amalgam Methyl Hg - Reacted Toxic Form/Poison Vapor - Detectable


Scientific Facts:     

High levels of Hg produce toxic effects. Hg vapor is minute / undetectable. Blood Hg increases upon removal of amalgam. Dental personnel have greatest exposure without evidence of decreased health. True hypersensitivity to amalgam = allergic reactions or lichenoid lesions.


Sources of Mercury Exposure in Dental Office: (Very Important)      

Amalgam raw materials stored for use. Mixed, unhardened amalgam during trituration and insertion. Amalgam scrap. Amalgam undergoing F & P. Amalgam being removed. Mercury leakage of amalgam capsules.

N.B: Once the amalgamation reaction is completed, only extremely minute levels of mercury can be released and those are far below the current health standard.


The Hazards From Mercury in Dentistry is Mainly Three Folded: (Very Important) 1- Systemic absorption of mercury through direct contact with the skin. 2- Inhalation of mercury vapor given off at room temperature. 3- Inhalation of air borne particles of mercury contaminated particles.

165


Historical Issues:   

First Amalgam War 1985 Huggins DDS “It’s All In Your Head” 1990 60 minutes Program “Poison In Your Mouth” Anti-amalgamists

 Anti-amalgam Claims:       

Neurotoxicity. Renal Dysfunction. Birth Defects. Arthritis. Multiple Sclerosis. Chronic Fatigue. Etc, Etc, Etc...

 Others Add Too!!       

Candida Infection. Hodgkin’s Disease. Mononucleosis. Depression. Ulcers. Epilepsy. Etc, Etc, Etc...


Adverse Reaction to Mercury Toxicity:  

Sensitization (hypersensitivity) Mercurialism (Symptoms)

166


Symptoms of Mercury Toxicity:          

Insomnia Physical weakness Irritability Loss of memory Impaired vision Nervous excitability Headaches Depression Speech disorders Muscular tremors


Dental amalgam safety:

Pregnant women: Mercury effects development of fetal brain and lead to: 1- Lowered intelligence. 2- Impaired hearing 3- Impaired coordination.

 Should amalgam be used during pregnancy? It is known that mercury can cross the placenta form mother to fetus and can also be detected in breast milk but this does not mean amalgam filling should be avoided during pregnancy or breast feeding. There is no evidence of any link between amalgam and mercury poisoning in infants and fetuses.


Threshold Limit Value ( TLV ) for Mercury Vapor is 0.05 mg (50 µg/m3): (Very Important) This concentration of mercury vapor represents the maximum level of mercury vapor in which a person can work for 40 h/week without demonstrable health risks.


Mercury Toxicity: Although the hazard is present, there have been NO REPORTS OF MERCURY VAPOR TOXICITY IN DENTAL OPERATORIES

167


Factors Affecting Mercury Leakage of Amalgam Capsules: (Very Important) 1234-

Type of capsule (single use or reusable capsule). Mixing time (especially with high speed amalgamator). Mixing speed. Temperature. Amalgam Personal hygiene: Never wear jewelry, mercury combines readily with silver and gold.


In Case of A Mercury Spill: 123456-

Never vacuum or broom. Put on rubber gloves. Keep room cool and ventilated. Use eye dropper, sponge or index cards disposal to soak up mercury beads. Put in sealed plastic bag with gloves and sponge used for pickup. Take HHW sit for proper disposal


Jorgensen Method of Checking Leaky Amalgam Capsule: Winding adhesive plaster around Capsule  trituration  inspection of the sticky surface of the plaster for mercury droplets.


Methods of Detection of Mercury Vapor at Dental Operatory: (Very Important) 1- Direct reading portable instrumentation (portable mercury spectrometer). 2- Mercury absorption procedures: collecting systems  analytical lab. 3- Mercury dosimeter

 Materials: a- CadiumSulphide. b- Palladium Chloride. c- Gold film.

168


Evaluation of Mercury Exposure Levels:  In the working environment: 50 µg/m3  In biological fluids:    

Urine : 150 µg/L

Saliva : 150 µg/100 mL Blood : 0.1 mg/100 mL Hair and Nails : 7 ppm

 Amalgam waste management.


Mercury-free direct metallic restorations: (Very Important) 1- Gold Foil. 2- Gallium. 3- Thermite Glass Ionomer (silver reinforced glass Ionomer).


Amalgam replacement (Ethical & Scientific issues)  Shouldn’t I?  

Many people want to replace their silver fillings because they have heard that there is medical risk from the mercury in the silver fillings. There are no clinical studies to prove that there is any risk in having a silver filling, so this should not be a reason for their replacement.

 Ethics: 



Unless new and compelling evidence is presented to the contrary, dentists cannot ethically tell patients that dental amalgam is a health hazard or that removal of amalgam restorations will benefit their health. When clinical research demonstrates that tooth-colored restoratives are as economical and effective in the long-term as dental amalgam, switch.

169


Dental Mercury Hygiene Recommendations (ADA):                 

Store in an unbreakable tightly sealed containers. Use non-touch technique for amalgam handling. Work in well-ventilated spaces. Avoid carpeting dental operatories (decontamination is not possible). Avoid heating mercury or amalgam. Use water spray and suction when grinding amalgam. Do not use ultrasonic amalgam condensers. Perform yearly mercury determination on all personnel regularly employed in dental offices. Have periodic mercury vapor level determination in operatories. Alert all dental personnel with the potential hazards of mercury during handling dental amalgam. Clean up any spilled mercury immediately. Use tightly closed capsules during amalgamation. Perform all operation involving mercury over areas that have impervious and lipped surfaces. Eliminate the use of mercury containing solutions. Use an amalgamator with completely closed arm. If possible, recap single use capsules after use and properly dispose them. Remove professional clothing before leaving the work place.


Conclusions:      

Continue to use amalgam unless esthetics is a concern. Use conservative preparations. Use resin sealants for non-carious fissures. Monitor research on bonded amalgams. Practice safe mercury hygiene. Stay informed!


Amalgam Restrictions:    

None in the United States. Sweden, Denmark, and Germany have proposed restrictions on amalgam use The intent is to reduce the environmental release of Hg , it is not due to amalgam restoration danger. Environmental concerns may limit our usage, not the “mercury poisoning” of our patients. 170


Revision: 1- The type of amalgam used in deep cavities is: a- Spherical amalgam. 2- The least amount of toxicity with amalgam is to the: a- Patient. 3- Put the wastes of amalgam in: a- Sulphide solution. 4- The most effective source of mercury toxicity is: a- Inhalation of mercury vapor. 5- Amalgam is contraindicated in: a- Patients with mercury hypersensitivity. 6- The most probable way of inhalation mercury in the dental office is: a- During condensation. 7- One of the future concerns that might discourage the use of amalgam is: a- Environmental concerns.

171


Student Notes:

172

173

Cavity Sealers, Liners & Bases
Objectives: By the end of this lecture, the student should: 1- Recognize the protective functions of enamel and dentin. 2- Discuss the problems associated with loss of hard tooth structure. 3- List the different types of insults to the dentin/pulp organ. 4- List and identify the difference between sealers and their indications. 5- Identify different types of sealers, and clinical implications of its using. 6- List and identify the difference between different types of liners and their indications. 7- Identify different types of liners and clinical implications of its using. 8- List and identify the difference between different types of bases and their indications. 9- Identify different types of bases and clinical implications of its using. 10- Explain how to determine the amount of required dentin-pulp protection. 11- Explain clinical implications of how to use the sealer, liner and base individually or combined together. 12- List types of permanent restorative materials which can be used and it’s compatibility between each of them and each type of sealer, liner or base. 13- Talk about biodentin and MTA.

174

Cavity Sealers, Liners & Bases
Definitions:  Cavity sealer: Seals all of the cavity preparation, acts as a barrier to leakage.  Cavity liners: A cement or resin coating of minimal thickness(less than 0.5mm), acts as a physical barrier.

 Cavity bases: Materials used to replace missing dentin, used for bulk build-up, acts as a thermal barrier.

 Cavity sealers: Provide a protective coating for freshly cut tooth structure of the cavity preparation. E.g. o Varnishes. o Adhesive sealers.


Cavity Sealers:  Varnishes:      

Copal varnish. Apply just before amalgam. Apply with cotton pellet. 2 thin layers. Air dry between layers. Will provide a short-term seal, corrosion of amalgam (gamma 2 phase) will then form a seal.

 Adhesive sealers: 

Acid etch 15 seconds, rinse, leave tooth slightly wet, apply bond resin, air dry, apply 2nd coat, air dry, light cure 10-20 seconds.

175


Cavity liners:  

A liner is a material applied to dentin to act as a barrier against irritation from the final restorative material and/or the effects of acid etching. A liner is approximately 0.5mm thick. Liners are placed with minimal thickness, usually less than 0.5mm, provide a seal, adhesion to tooth structure and antibacterial action. E.g. o Calcium hydroxide. o Glass Ionomer.

 Calcium hydroxide: Mix equal amounts of catalyst and base, apply sparingly with applicator, (self-cures in 2-3 minutes), cover with G.I.

 Glass Ionomer: Mix liquid and powder to give a “Dycal-like” consistency, apply with applicator, light cure 20 seconds.

 Liner mixing instructions:   



Always follow the manufactures instructions. With glass Ionomer cements you may vary the powder/liquid ratio slightly with significantly altering the physical properties. With GI mix the powder and liquid all at once, not in gradual amounts. Calcium hydroxide is very weak and dissolves over time so use just enough to cover a direct exposure then cover the calcium hydroxide with a layer of glass Ionomer to protect it and seal it in place. Chemical-cured calcium hydroxide takes about 5 minutes to set in the mouth.

176


Cavity bases: 



A base is a dentin substitute which is applied in a thicker layer (1 - 1.5mm) in order to provide: o Thermal protection. o Protection against harsh chemicals. Used as dentin replacement materials, allowing for less bulk of the restorative material or blocking out undercuts for indirect restorations. E.g. o Zinc-oxide eugenol. o Zinc phosphate. o Polycarboxylate. o Glass Ionomer.

 Base mixing instructions: •

Zoe: Mix to a thick, slightly sticky consistency, pack in place.

•

ZnPh /Polycarboxylate: thick, packable mix.

•

G.I: Mix according to manufacturer’s instruction and pack in place or apply in a number of thin layers curing each layer.



When mixing Zoe you will find that the liquid will absorb a large volume of powder. Mix enough powder into the liquid to produce a consistency that may be rolled into a ball but still be moist enough to stick to the tooth surface to provide a good seal. Zoe is an excellent short-term temporary restorative material as it sedates the pulp as well as providing a good seal. To place the ZOE in the tooth preparation, dip your plugger in dry zinc powder to prevent the slightly sticky mix from sticking to the instrument. You will have to do this often during placement. When mixing light-cured Ionomer cement dispense the recommended amount of powder/liquid and mix all the powder into the liquid at once. If the mix is a little too thick to apply with a Dycal applicator you may mix a small amount of excess liquid to give it the desired consistency. Just remember the thinner the mix the weaker it is.

 



177


Approximate thickness of liners and bases:   

Luting cement: 20 - 30mu. Liner: about 0.5mm. Base: 1 - 1.5mm.


Thermal conductivity of liners & bases (cal/sec/cm2):      

E/D: 0.0015-0.0022 Zoe: 0.001 ZnPh: 0.003 Resins: 0.005-0.0008 Amalgam:0.04-0.06 Gold: 0.75-1.10






Liners and bases compressive strength:     

G.I: 20,000 psi + ZnPh: 17,000 psi PCA :10,000 psi ZOE: 2,000 psi Ca(OH): 500-1500 psi

NOTES: The difference between Liners & bases is the thickness of the material not the material. It is better to over-fill rather than under-fill the cavity as you can remove excess cement easily with a bur or diamond point.


Glass Ionomer cement:       

Strong. Fluoride releasing. Relatively kind to the pulp. Adheres to dentin. Good thermal protection. Chemical and light-cured. Easy to handle.





178

NOTES When using cement as a base, make sure you leave enough depth for a strong restoration. G.I. is next to impossible to remove, Polycarboxylate cement chips off easily.


Guidelines for basing, lining & sealing:    

Maintain sound dentin. You do not have to base to the “ideal” cavity depth. Use the minimum layer of liner/base to achieve desired results. No evidence for use of resin sealers under metallic restorations.

179


Revision: 1- Dentin bridging is induced by: a- CaOH. 2- The best liner used if the Dentin is less than 1.5 mm is: a- Glass Ionomer or CaOH. 3- Glass Ionomer sealant shows: a- Lower retention than Resin. 4- In medium sized cavities, the function of the linear is to: a- Seal the dentinal tubules. 5- Liner function is: a- Physical barrier. 6- Decreased filler content in sealant causes: a- Increase wear. 7- Early loss of sealant is most probably due to: a- Moisture contamination. 8- Sealant is indicated in: a- Primary tooth with incipient caries. 9- Sealer resin composition: a- Bis-gamma.

180


Student Notes:

181

182

Temporary (Provisional) Restorations
Objectives: By the end of this lecture the student must be able to: 1- Define temporary restorations and describe situations required theses temporaries. 2- Identify functions of temporary restorations and describe factors affecting their selection. 3- List & compare different available temporary restorative materials and identify how to select the most appropriate one for each case. 4- Identify the requirements for an ideal temporary restoration. 5- Describe the techniques of fabrication of Acrylic Resin temporary restorations.

183

Temporary (Provisional) Restorations
Definition: It is a short term restoration designed to replace the missing portion(s) of the tooth structure till arrangement for placement of the final (permanent) restoration.


Situations that require temporary restorations: (Very Important) 1234-




Caries control (high risk patient; acute caries). Deeply seated carious lesion (direct or indirect pulp capping). Time restriction by the patient and/or the operator. Restorations that require laboratory work (e.g. inlays & onlays). NOTE: 5- Sealing of access cavities during endodontic therapy. Temporary restorations can be used as…Analgesic, Pain relieving, 6- Tooth on pain (especially with irreversible pulpitis). Soothing effect, Obtundant, Balitev restorations till the pain Functions of temporary restorations: (Very goes (all have the same meaning). Important) 123456-

Protection of the dentin-pulp organ during visits. Sedation of the dentin-pulp organ. Restoration of occlusion. Protection of the periodontium. Putting the tooth into function. Protection of the tooth from fracture.


Factors affecting the selection of temporary restoration: (Very Important) 123456-

Type of final restoration. Vitality of the tooth. Size and location of the cavity. Time interval expected for dressing. Position of the tooth. Forces of occlusion

184


Rampant Caries: Definition, Criteria, Diagnosis, Management (REFER)


Available temporary restorative materials: 1- Zinc oxide / eugenol: Conventional; Resin-based ZO/E (IRM); Neo-eugenol ready made TF! 2- Zinc phosphate cement. 3- Polycarboxylate cement. 4- Glass Ionomer cement. (see page 190) 5- Acrylic resin temporaries.


Zinc Oxide & Eugenol:  Advantages: 1234-

Good initial seal ability. Obtundant (at shallow & moderate depths). Caries control restoration. Easily applied & easily removed!

 Disadvantages: 1234-

Low abrasion resistance leads to loss of contour. Low strength properties leads to fracture. Objectionable color. Irritating to the pulp& interacting with the composite restoration thus preventing it from binding to the tooth.


Resin Temporaries (AR inlays & onlays):  

It is done for inlay cavity, till delivering the cast inlay. It will maintain the patient in comfort, protect and stabilize the prepared tooth.

185


Requirements of ideal temporary restoration: (Important) 1234567-

Non-irritating, protect the prepared tooth. Protect & maintain the health of the periodontium. Maintain position of prepared, adjacent & opposing teeth. Provide accepted esthetic, phonetic & masticatory functions. Easily cleaned by the patient. Adequate strength & retention to withstand the applied forces. Easily fabricated, applied, removed & inexpensive!


Techniques of fabrication of Acrylic Resin temporary restorations: A- Indirect technique. B- Direct technique.

A- Indirect technique: •

Advantages: (Important) 1- Better marginal accuracy than the direct technique, less pulpal irritation, good oral hygiene & good periodontal health. 2- Better visibility & accessibility to block and correct the undercuts on prepared & adjacent teeth. 3- Avoid possibility for irritation from acrylic resin monomer. 4- Checking & adjustment of the preparation before final restoration (or impression?)

186

•

Technique of fabrication: 1- Preoperative alginate impression after filling of large defects with utility wax.  One or two teeth = Quadrant impression.  More than two teeth = full arch impression. o Keep the impression aside after wrapping in a wet paper towel. 2- Post-operative alginate impression is taken & poured in fast-set plaster. 3- Block the voids with utility wax & remove positive blebs with sharp knife if present! 4- Remove undercuts at gingival & soft tissue areas. 5- Try the plaster cast in the pre-operative impression. 6- Mix the tooth colored AR following the manufacturer instructions. 7- Pour the AR at the preparation area at the impression. 8- Seat the plaster cast in the impression. 9- Wrap the impression & cast with rubber band to avoid distortion & let it set in warm water. 10- With suitable bur (no. 271) or acrylic stone, trim any excess AR and Try the temporary on the cast. 11- Try it on the tooth at the patient mouth, make the fine adjustment &occlusal correction then finish & polish it! 12- Keep it aside for cementation with temporary cement after final impression is taken.

B- Direct technique: •

Advantages: (Important) 1- Quick. 2- Less steps & materials required.

•

Disadvantages: (Important) 1234-

Locking of AR in undercut areas at prepared & adjacent teeth. Improper marginal adaptation “Sequela!” Improper contouring. Pulpal irritation due to AR monomer!

187

•

Technique of fabrication: 1- Preoperative alginate impression is taken and tried after the preparation. 2- Eliminate the undercut areas at the impression. 3- Mix the AR, apply it in the impression at the preparation area, place the impression on the teeth after painting of the preparation with separating medium & seat the impression properly. 4- Remove the impression at rubbery stage; usually the temporary will remain on the tooth. 5- Remove the temporary with spoon excavator, let it to set aside. 6- Trim it, try it & make adjustments; then make finishing, polishing & temporary cementation as mentioned with indirect technique.

188


Revision: 1- An Advantage of ZnO over zinc phosphate is: a- Obtundant to the pulp. 2- An advantage of ZnO as temporary filling: a- Good initial sealability and obtundant.

189


Student notes:

190

191

Glass Ionomer Restorations
Objectives: By the end of this lecture the student should: 1- List the advantages and disadvantages of the glass Ionomer restoration. 2- Be acquainted of clinical indications and clinical contraindication of using glass Ionomer. 3- Be familiar with the basic composition and structure of glass Ionomer. 4- List and compare between different types of glass Ionomer cements. 5- Explain clinical implications of using conventional glass Ionomer, resin modified glass Ionomer and poly-acid modified composite resin restorations. 6- Be acquainted of properties of glass Ionomer cements; a- Hydration and dehydration. b- Biocompatibility. c- Setting shrinkage. d- Bonding to tooth structure. e- Wear properties. f- Strength properties. g- Fluoride release/uptake. 7- Compare ways of preparing teeth for glass Ionomer and identify the best approach. 8- List and compare the different manipulat1on techniques. 9- Describe the technique of placing the different types of glass Ionomer cements. 10- Recognize problems with glass Ionomer cements.

192

Glass Ionomer Restorations
Definition: Glass Ionomer: “glass” refers to the glassy ceramic particles and the glassy matrix (non-crystalline) of the set material, while “Ionomer” refers to ion-cross linked polymer.


History of Development:  United Kingdom 

Wilson and Kent 1972.

 ASPA (Aluminum Silicate Polyacrylic Acid)   

First commercial product. Alumina-silicate Polyacrylic acid. Combined benefits: o Silicates: Translucency & fluoride release. o Polycarboxylates: Adhesion & biocompatibility.


Early glass Ionomer:      

Poor esthetics. Rough surface. Prolonged setting reaction. Poor wear resistance. Vulnerable to hydration extremes. Handling difficulties.

193


Modifications: 

  

Refined formulation: o Addition of Tartaric acid. o More reactive acids. Improved packing. Metal modification. Addition to resin.


Advantages:     

Inherent (chemical) adhesion to tooth structure. Fluoride release (anti-cariogenic). Coefficient of thermal expansion (CTE) similar to tooth structure. Biocompatible. Minimal healthy tooth structure removed.


Disadvantages: 

    

Sensitive to moisture and desiccation: o Moisture: it absorbs water quickly from the saliva therefore the matrix will be fragile and it will become weak causing degradation of the particles so it gives a rough surface. o Desiccation: it will lose water causing the formation of cracks. Low fracture toughness. Low flexure strength. Low wear resistance. Relatively poor esthetics. Solubility and disintegration.

194


Indications: 



    

Direct restorative: o Class V. o Root caries. o Class III. o Pediatric dentistry. Resin modified version o Tunnel preparations. o Atraumatic restorative treatment (ART). Luting agents. Liners. Caries control. Core block-out. Occlusal sealant.


Contraindications: 

Stress-bearing area in permanent teeth: o Class I, II & IV.


Physical properties:    

    

Moderately hard, brittle material. Relatively high compressive strength. Relatively low tensile strength. Low: o Fracture toughness. o Fracture strength. o Wear strength. Expand under moist conditions. Contract under dry conditions. Tensile stress is 1/10 of its compressive stress. Lesser good color stability. Coefficient of thermal expansion is 0.8 that of tooth.

195


Chemical composition: A- Powder:      

Ion leachable calcium fluorosilicate glass. Silicon dioxide. (41.9%) Calcium fluoride. (28.6%) Aluminum phosphate. (12%) Aluminum fluoride. (8%) Sodium fluoride. (9%) o These powders are combined and fused at a temperature 1100- 1500°C for 2 hours in the presence of fluoride as flux to reduce their fusion temperature. o The molten gas is poured on steel tray to fragment it. o The fragments are crushed, milled and powdered in particle size range 20 –50 microns. o For cementation purpose, a particle size of 13 – 19 micron is optimal.

B- Liquid:    

Aqueous solution of polymers and copolymers of acrylic acid. A copolymer is a chain consisting of 2 molecules. In GI, such a copolymer might be a Polyacrylic acid + itaconic acid segment. Polyacrylic acid is the most important acid in formation of cement matrix with 3 other acids which are: 1- itaconic acid: a- Increases reactivity of the liquid. b- Decreases tendency to gelation. c- Decreases viscosity.

196

2- polymeric acid: a- Cause the cement to harden as it is stronger than Polyacrylic acid. b- Lose its moisture sensitivity faster. c- It allows the use of more conventional, less relative glasses which result in a more esthetic final set cement. 3- Tartaric acid: abcd-

Increase working time. Improve hardening properties. Strengthens and hardens cement. Sharpness set.

C- Water: Acts as a reaction medium and hydrates the reaction products.

• Water gain: 12345•

Dissolution of polysalts and loss of adhesive potentials. Decrease strength. Solubility and disintegration of restoration. Destruction of translucency. Erosion of weakened surface.

Water loss: 12345-

Surface micro-cracks. Increase opacity. Increase staining and micro-leakage. Poor esthetics. Weakened restoration.

197


Classification according to compositional forms: A- Water mixed:  

Poly acids are vacuumed or freeze-dried and incorporate into powder. These cements are called water mixed or water hardened.

•

Benefits:  

Maximize shelf life. Reduce viscosity.

B- Non water mixed GIC: 

Liquid contains polyacids: o These products are somewhat viscous. o May exhibit gelation of the liquid. N.B. the bottles of liquid of these forms should not be refrigerated because they will become too viscous for use.

C- combination:   

Powder contains dehydrated Polyacrylic acid. Liquid contains Polyacrylic & tartaric acid. Viscosity and shelf life of these cements are intermediate to the other 2 types.


Classification of GI according to use: A- Type I (luting):    

Use: cementation of crowns, bridges, inlays & orthodontic appliance. Setting rate: fast set. P/L ratio = 1.5:1. Film thickness: 25 microns.

198

B- Type II (restorative): I.

Type II (1) (esthetic restoration):  

II.

Use: esthetic restoration. P/L ratio= 3:1.

Type II (2) (reinforced restoration):   

Use: when physical properties are more important than esthetics. Setting rate: fast set. P/L ratio= 3:1.

C- Type III (lining or base): I.

Lining:  

II.

Use: thermal; barrier under metal restoration. P/L ratio= 1.5:1.

Base (dentin substitute):  

Use: in combination with composite in lamination technique (Sandwich technique). P/L: 3:1.

D- Type IV (visible light activated liners/bases):   

They bond to resin as well as to dentine. Less moisture sensitivity. Light activated for easier clinical handling.

199

Note: The type of glass Ionomer used in cases of increased salivation is Visible light activated.


Setting reaction:  Complex acid-base reaction:   

Glass (basic) + polyacid. Forms salt hydrogel. H2O reaction medium.

 Three phases:   

Ion-Leaching phase. Polysalt-Gel phase. Hydrogel.


Material-Related Variables: A. Fluoride release. B. Adhesion. C. Biocompatibility. D. Optical properties.

 Fluoride re-charging of Glass Ionomers:   

Fluoride release exponentially decays to low levels (0.5- 2.0 typically). Re-charging = F absorption from other sources to GI materials for re-release later. It occurs when F can readily diffuse from high to low concentration.

 Re-charging strategies: 1- Use daily F rinses to provide F source for re-charging. 2- Use F toothpastes for re-charging. 3- Use topical Fluorides for re-charging.

200

 Properties: 1234-

High F concentration produces immediate increase in F levels of restorations. Once re-charging source is removed, re-release immediately begins. High F release occurs for short period of time and quickly goes back to the original level. Value of F re-charging has never been demonstrated clinically.

 Adhesion to tooth structure: 

Adhesion: is the force that causes unlike materials to adhere to each other. o A full 80% of the ultimate bond strength of the GIC to tooth structure develops within the first 15 minutes following placement. o GIC chemically bonds to enamel and to a lesser extent to dentine and cementum. o GI, inter-diffuse to dentin and establish a micromechanical bond with collagen fibrils following hybridization principle. o Chemical bonding by ionic interaction of carboxyl groups of polyalkenoic acid from GI with Ca of hydroxyapatite. o Adhesion is initiated by the polyalkenoic acid when freshly mixed material contacts tooth surface. o Phosphate ions are displaced from appetite by carboxyl groups. o Each phosphate ion takes Ca ion with it to retain electrical neutrality. o An ion enriched layer firmly attached to the tooth structures is formed & called (Caphosphate polyalkenoic crystalline structure)

 Biocompatibility: 



All soft tissues have a favorable response to GI, It is resistant to plaque. Bacterial plaques (especially mutans streptococcus) fail to survive on the surface of GI due to the presence of fluoride. It is biocompatible with tooth tissues, although it is acid containing, because: 1- Its acids are weak and have high molecular weight, so has less diffusion through dentinal tubules to the pulp. 2- It has minimum temperature rise compared to other materials. 3- It is ion exchange adhesion that prevents micro-leakage and so it is valuable in isolation of active carious lesions. In case of deep preparation, CaOH is applied to the area next to the pulp before GI application because of the low surface PH of traditional GI in the first 60 minutes of setting.

201

 Post-Operative Sensitivity (Luting cements):    

GI can cause post-operative sensitivity when used as luting agent. Clinical studies show no increase in sensitivity when properly used. Conventional GI vs. Zinc Phosphate: o No difference. Conventional GI vs. RMGI: o No difference.

 Optical Properties:   

Most GI is more radio-opaque than dentin and several GI are more radio-opaque than enamel in its insertion but its radio-opacity decrease after a period of time due to solubility. Early GI was extremely radio-opaque because of their higher fluoride content which was necessary to improve their handling properties. Translucency generally improves over the first 24 hours but does not reach a maximum until at least a week after placement of GIC restoration.

 Sensitivity to moisture & desiccation:  

Most opinions consider GIC sensitive to moisture during the first 24 hours (till the formation of stable less soluble Al Polycarboxylate). Others recommend that GIC is protected from moisture for the 10-30 minutes after initial placement.

 Effect of moisture contamination: 

Early contamination prevents Ca & Al ions from leaching out of the aqueous cement phase and are prevented from forming Polycarboxylates, this causes the matrix to turn chalky & erode easily to produce a rough surface& decrease surface hardness.


Cavity design:   

No need for retentive features because of its adhesive potentials. No need for extensions for prevention because of its cariostatic effect. In deep cavities, a layer of CaOH is needed for pulp protection.

202


Manipulation:  Dispensing & mixing: Glass Ionomer is available in 2 forms: 1- capsule for mechanical mixing:  

Provide consistent & satisfactory P/L ratio. Ensures optimal physical properties.

2- Powder & liquid for hand mixing: The mixed material should be transferred to disposable syringe for positive placement in the cavity.

 Placement technique: 1- The cavity is conditioned by acid 10% for 10 seconds then Polyacrylic dried without dehydration and washed, isolated. 2- The restoration is then hand mixed or mechanical mixed. 3- Place restoration into the depth of the cavity first and continue expelling it while withdrawing the syringe. 4- Apply the matrix for final positive placement. 5- Allow the restoration to set. 6- Remove the matrix and cover the restoration with a layer of sealant which may be light cured bonding agent or 2 layers of cavity varnish. 7- Trim the excess restoration while the sealant is still liquid by a sharp blade or by slowly rotating the bur in a direction from the restoration to the tooth. 8- If the sealant is disturbed during contouring then apply a second layer. 9- Trim any excess sealant. 10- Contouring & polishing is done after 24 hours under air / water spray with fine diamond in the beginning then aluminum oxide discs for finishing.

203


Metal Reinforced Glass Ionomer: It is a conventional GI which is modified by filler particles to improve: 1- Strength. 2- Fracture toughness. 3- Resistance to wear. On the expense of amount, fluoride release & bond strength to tooth structure.

 Variants of Metal Reinforced Glass Ionomer: 1- Silver alloy admix: in which silver amalgam alloy is mixed with type II GI powder. 2- Cermet: In which inclusion of Ag particles to glass powder by fusion through high temperature sintering.


Resin Modified Glass Ionomer:  

First developed as liners. It is a hybrid material of conventional GI with addition of small amount of light curing resin.

 Composition: A- Powder: It is similar to conventional GI plus photo-activated accelerator.

B- Liquid: It is similar to conventional GI plus methacrylate groups grafted and / or hydroxyethylmethacrylate (HEMA).

C- And / or water.

204

 Matrixes: 1- Acid-Base Matrix: mixing the powder and liquid initiates the acid-base reaction of conventional glass Ionomer that hardens and strengthens the formed matrix (responsible for fluoride release and bonds with tooth structure). 2- Polymerization Matrix: exposure to visible light initiates polymerization reaction of the methacrylate groups which are responsible for the formation of polymerization matrix (resin matrix from free radicals).

 Types of cure: 1- Dual Cure: light initiation followed by acid-base reaction (chemical). 2- Conventional (auto-cure): chemical cure of acid-base reaction.

 Compared to Glass Ionomer:   

    

Fluoride release is almost equal. Fluoride is released in the first few days to weeks and then drops to a low level that is released for a long time. Wear resistance
205


Compomers: “Composite & Glass Ionomer”  Polyacid-modified composite resin.  Matrix: o Dimethacrylate monomer.  Carboxylic groups.  Filler: o Ion-leachable glass.  No water.

 Setting reaction:     

Free radical polymerization reaction (similar to resin composites). Resin-based adhesives. No chemical bond to tooth structure. Low levels of fluoride release. Delayed acid-base reaction

 Compomers in Dentistry: 



Direct restorations: o Restoratives. o Flowables. Cements.

 Advantages:    

Easy to place and polish. Some fluoride release. More esthetic than GI. Better mechanical properties than GI.

206

 Disadvantages:   

Inferior mechanical properties o Compared to composite. Less fluoride release than GI o Minimal recharge. No chemical bond to tooth structure.

 Indications:  



Esthetics. Areas of lower stresses: o Class V. o Class III. o Pediatrics. Conservative class I & II.

 Contraindications:    

Stress bearing areas: o Permanent class I or II. Increased wear. Loss of marginal integrity. Poor isolation.


Giomers:   

It is a new type of restorative material. Giomer is a hybrid of the word “Glass Ionomer” & “Composites”. It’s available in 13 shades and is supplied in syringes.

207

 Properties: 



     

As GI: o Fluoride release. (long term release was lower than that of other material ) o Fluoride recharge. As composite: o Excellent esthetics. (If polished with soflex disks, had smoother surface than GI ) o Easy polish-ability. o Biocompatibility. Particles are made of fluorosilicate glass that has been reacted to Polyacrylic acid prior to being incorporated into resin. The pre-reaction can involve only the surface of the glass particles (called surface prereacted glass Ionomer or S-PRG). Giomer are similar to Compomer and resin composite in being light activated and requiring the use of a bonding agent to adhere to tooth structure. No chemical bond to tooth structure. More research needed. Only one Giomer is commercially available “Shofu”.

 Indications of Giomers: 1- Class I & V. 2- Cervical erosion. 3- Root caries.

208


Revision: 1- The liquid used in traditional glass Ionomer is: a- Polyacrylic acid. 2- The common acid between glass Ionomer and Polycarboxylate cement is: a- Polyacrylic acid. 3- The cement that has anticariogenic effect is: a- Glass Ionomer. 4- An advantages of light cured glass Ionomer over chemical cured is: a- Form second matrix. 5- Release of fluoride from glass Ionomer: a- F released from the matrix. 6- What does dual cure mean: a- Light cure and self cure. 7- The type of Glass Ionomer that resembles the Composite is: a- Compomer. 8- The best temporary restoration in endo filling is: a- Glass Ionomer. 9- The acid not used in glass Ionomer is: a- Citrate acid. 10- The Powder of Glass Ionomer is: a- Aluminosillicate glass. 11- after recharge of glass Ionomer with F a- 1 to 2 days. 12- The best way to recharge Glass Ionomer is: a- Topical fluoride.

209

13- The sandwich technique is: a- Glass Ionomer below composite. 14- Glass Ionomer bond to enamel better than dentin due to: a- Higher Inorganic content in enamel. 15- In Glass Ionomer, fluoride is released from: a- The Matrix. 16- Glass Ionomer is superior to resin in that it's: a- Anticariogenic 17- Which application that needs advantage of mechanical adhesion of glass Ionomer the most: a- Class V. b- Liner. c- Base. d- Cement. 18- Which application that needs advantage of fluoride release of glass Ionomer the most: a- Base. b- Liner. c- Root treatment. d- Shy filling material. 19- ART is a shortcut for: a- Atraumatic restoration technique. 20- What is the purpose of ART: a- Prevention and treatment of caries with minimal instrumentation.

210


Student Notes:

211

212

Composites
Objectives: By the end of this lecture students should be able to: 1- Identify the various types of Composite resin materials. 2- Record and discuss the properties of Composite resin materials. 3- Recognize and explain indications and contra indications of Composite restoration. 4- Recognize and explain the advantages and disadvantages of Composite resins. 5- Correlate the material properties to indications and contra indications.

213

Composites
What is a composite? Materials with two or more distinct substances e.g. metals, ceramics or polymers.


What is a dental composite resin? A continuous polymeric or resin matrix in which an inorganic filler is dispersed. The strong bond between the organic resin matrix and the inorganic filler is achieved by coating the fillers with a Silane coupling agent.


Composition: 1- Resin matrix:    

Monomer. Initiator. Inhibitors. Pigments.

2- Inorganic filler:   

Glass. Quartz. Colloidal silica.

3- Coupling agent.

214


Monomers:  Bis-GMA: •

Extremely viscous: 

•

Large benzene rings.

Lowered by adding TEGMA:    

Freely movable. Increases polymer conversion. Increases crosslinking. Increases shrinkage.

 Shrinkage:  

2-7%. Marginal gap formation.


Filler particles:  Crystalline quartz:  

Larger particles. Not polishable.

 Silica glass:    

Barium. Strontium. Lithium. Pyrolytic. o Sub-micron.

215


Functions of inorganic filler:  Enhances physical properties by:  

Increasing strength. Reducing the liner coefficient of thermal expansion.


Filler particles:  35 to 71 % by volume.  50 to 86% by weight.  Increase fillers, increase mechanical properties:    

Strength. Abrasion resistance. Esthetics. Handling.


Functions of Silane coupling agent:  

Increases strength. Reduces solubility and water absorption.


Visible-light activation:  Camphorquinone:   

Most common photo-initiator. Absorbs blue light. 400-500 nm range.

216


Classification system:  Based on particle size: 1234-

Traditional. Micro-filled. Small particle. Hybrid.

 Based on filler size, amount and composition of inorganic filler: 1- Macro-filled (conventional), 75% - 80%, 8 Um, Quartz. 2- Micro-fill (polishable), 35% - 60%, 0.001 - 0.004 Um, silica or barium glass. 3- Hybrid composite, 75% - 85%, 0.4 – 1 Um combination.


Traditional (Macro-filled):  

    

Developed in the 1970s. Crystalline quartz. o Produced by grinding or milling. o Large (8 to 12 microns). Difficult to polish. o Large particles prone to pluck. Poor wear resistance. Fracture resistant. Examples: adaptic, concise. Suitable for class III, IV and V.

217


Micro-fills:  





Better esthetics and polishability. Tiny particles: o 0.04 micro colloidal silica. o Increases viscosity. Lower filler content: o Inferior properties:  Increased fracture potential.  Lacks coupling agent.  Lacks radiopacity. Suitable for class III, V.


Small particle:     

1- 5micron heavy-metal glasses. Fracture resistant. Polishable to semi-gloss. Suitable for class I to V. Example: Prisma-Fil.


Hybrids:  

   

Popular as “all-purpose”: o Aka universal hybrid, micro-hybrids, micro-filled hybrids. 0.6 to 1 micron average particle size. o Distribution of particle size:  Maximizes filler loading. o Micro-fills added:  Improve handling.  Reduce stickiness. Strong. Good esthetics: o Polishable. Suitable: o Class I to V. Multiple available. 218


Nano-filled composite:  

Filtek Supreme (3M ESPE). Filler particles: o Filled: 78% weight. o Nanomers: 0.02-0.07 microns. o Nanocluster:  Act as single unit: 0.6- 1.4microns.


Composite variants:  

Packable. Flowable.

 Flowable composites: •

Marketed for:  

Class I, III, IV. Liner.

•

Particle size: similar to hybrid composites.

•

Reduced filler content: 

•

Reduces viscosity.

Flowable composites, low filler content:  

Disadvantage: o Have inferior physical properties such as low wear resistance and strength. Advantages: o Good wet ability and handling properties.

219

•

Uses: 1- Small class I restorations as pit fissure sealant. 2- Marginal repair. 3- As a liner under hybrid or packable composite.

 Packable composites: •

Marketed for posterior use. 

•

Increase in viscosity: o Better proximal contacts. o Handle like amalgam.

Subtle alteration of filler:   

Shape. Size. Particle distribution.

•

Similar resin chemistry and filler volume.

•

High filler, more viscosity: 

•

Affords a “feel” upon insertion, similar to amalgam (but some displacement of matrix band is possible).

They were developed to achieve two goals: 1- Easier restoration of proximal contact. 2- Similarity to handling properties of the amalgam.

220


Packable Vs. Hybrid composites: 



Similar: o Mechanical properties. o Wear properties. o Curing depths. o Proximal contacts. Drier, denser feel.


Another classification: 1- Homogenous. 2- Heterogeneous (precured composite).


According to mode of cure: 1- Chemical cured. 2- Light cured:  Longer working time.  Better color stability (less voids). 3- Dual cured (mainly luting cements).


Indications: 1234-

Class I, II, III, IV, V and VI restorations. Core buildups. Sealants and conservative composite restorations (preventive resin restorations). Esthetic enhancement procedures:  Partial veneers.  Full veneers.  Tooth contour modifications.  Diastema closures. 5- Cements (for indirect restorations).

221


Contraindications: 1- If the operating site cannot be isolated. 2- If all the occlusion will be on the restorative material.


Advantages: 123456-

Esthetics. Conservative tooth structure removal. Less complex when preparing the tooth. Insulative, having low thermal conductivity. Used almost universally. Bonded to tooth structure resulting in: o Good retention. o Lower micro-leakage. o Minimal interfacial staining. o Increase strength of the remaining tooth structure. 7- Repairable.


Disadvantages: 1- Polymerization shrinkage resulting in gap formation (usually on root surfaces). 2- More difficult, time consuming, and costly (compared to amalgam restoration) because: a- Tooth treatment usually requires multiple steps. b- Insertion is more difficult. c- Establishing proximal contact axial contours, embrasures, and occlusal contacts may be more difficult. d- Finishing polishing procedures are more difficult. 3- More technique sensitive. 4- Exhibit greater occlusal wear in areas of high occlusal stress. 5- High linear coefficient of thermal expansion resulting in marginal percolation if inadequate bonding technique is utilized.

222


Important properties: 1- Linear coefficient of thermal expansion (LCTE) dimensional change of a material per unit change in temperature. o The closer the LCTE of material to that of enamel, the less the chance there is for creating openings at tooth-restoration interface when temperature changes. 2- Water absorption. o Affected by amount of matrix. 3- Wear resistance: o Affected by filler particle size, shape, content and occlusal relationship. 4- Surface texture. 5- Radio opacity. 6- Modulus of elasticity: o Flexibility may perform in class V. 7- Solubility.


Polymerization of composite:  Polymerization shrinkage:   

Can’t be avoided. Main disadvantage of composite. Results in creation of polymerization stresses.

 Sequela (results) of polymerization shrinkage stress: 1- Transferred to the tooth and causes deformation, may result in enamel fracture. 2- Gap between resin and cavity walls post-operative sensitivity, micro-leakage and recurrent caries.

223

 Polymerization shrinkage factors: •

Tooth:    

•

Location. Size. C-factor Factors related to tooth: o C-factor: cavity configuration and stress development, it is the ration between bonded and un bonded surfaces o Flat surfaces. o Shallow cavities.

Composite:   

Formulation. Technique of insertion. Factors related to material: o Filler content: increase in filler content decrease in polymerization shrinkage. o Nano-filler technology. o Resin formulation. o Degree of conversion of monomer into polymer: increase in degree of conversion increase stress, however enhances mechanical properties. o Water sorption: decreases stress, however it deteriorates mechanical properties.

•

Bonding agent.

•

Curing technique: 

Factors related to curing: o Light energy = light intensity X time. o Light distance. o Rate of curing. o Mode of curing: light curing or chemical.

224

 Polymerization techniques:  

•

Use Flowable composite below packable composites to act as stress breaker. Open sandwich technique to seal cervical cavity in class II. Sandwich technique: use of glass Ionomer below composite in deep cavities.

Advantages of glass Ionomer:    

Reliable form of adhesion to dentin with little or no polymerization stress. Establishes chemical bond to composite. Anti-cariogenic. Volumetric reduction of composite shrinkage.

 Restorative techniques: 

     

Incremental filling: o Decrease polymerization material volume. o Reduce bonded to un-bonded surface ratio. o Minimal contact with cavity walls. Facio-lingual layering (vertical). Gingivo-occlusal layering (horizontal). Three site technique. Wedge shape layering (oblique). Bulk technique. Centripetal technique.

 Polymerization strategies: The idea is that we try to delay gel point (point of transformation of composite paste into solid) to allow some stress relaxation.

 Total light energy:  

Light intensity X time. Either begin with low intensity and then high intensity (soft start polymerization) or use low intensity for a long period of time.

225

 Mode of curing: Chemical cured composite resins offer less polymerization stress due to slower rate of curing.


Pre & post composite insertion steps: A- Pre-insertion Steps: 1- Isolation recommendations: -

Rubber Dam Isolation is Mandatory:  Failure to maintain a dry field will result in clinical failure.  Prevention of moisture contamination and protection of gingival tissues is of paramount importance.  Select shade before rubber dam application.

2- Bonding to Enamel & Dentin: -

Variations in Tooth Structure: o Enamel: more predictable bonding:  More homogeneous structure.  Higher inorganic content.  Higher surface energy. o Dentin: less predictable bonding:  Higher variability.  Higher organic content.

-

Enamel Composition: o Primarily inorganic:  Hydroxyapatite.

226

-

Enamel Bonding: o Developed by Buonocore-1955. o Etching:  Various acids: • Traditionally phosphoric acid.  creates micro-pores: • 5 – 50microns deep.  Increases surface energy.  Increases wettability.

-

Dentin Structure: o Dentin composition. o Dentinal tubules. o Changes in dentin structure. o Smear layer. o Dentinal wetness.

-

Dentinal tubules: o Radiate from pulp. o Largest near pulp.  2.5 microns at pulp.  0.8 microns at DEJ. o Concentrated near pulp:  45,000/mm2 at pulp.  20,000/mm2 at DEJ.

-

Tubule Composition: o Peritubular dentin:  Surrounds tubule.  Hypermineralized. o Intertubular dentin:  Between tubules.  Less mineralized. o Odontoblastic process. o Dentinal fluid.

227

-

Changes in Dentin Structure: o Sclerotic:  Normal aging.  Abrasion.  Erosion. o Reparative:  Caries.  Dental procedures. o Hypermineralization. o Less receptive to bonding.

-

Smear Layer: o Produced by instrumentation. o Composition:  Cut dentin debris.  Bacteria. o Reduces dentin permeability:  86%. o Thickness:  0.5 - 5microns. o Will not wash off. o Weak bond to tooth:  2 – 3MPa. o Very soluble:  Weak acids

-

Dentinal Wetness: o Increases:  Dentinal depth.  Removal of smear layer.  Historically, more difficult to bond

-

Dentin Bonding: o Development:  Seven generations.  Chronologic Classification.

228

 Currently available generations: •

Fourth Generation: 

•

Three-step Etch & rinse.

Fifth Generation: 

•

Two-step Etch & rinse.

Sixth Generation:  

•

Two-step Self-etch. One-step Self-etch: o Mix.

Seventh Generation: 

One-step Self-etch: o No mix

 Classification of newer systems:  

Interaction with tooth surface. Number of clinical application steps: 1- Etch & rinse i.e. total-etch. 2- Self-etch. 3- Resin-modified glass Ionomer.

•

Etch & Rinse (Three-Step):   

Conditioner. Primer. Adhesive resin.

229

-

Conditioner:  Chemical alteration of surface: o Acids: Phosphoric, Citric, Maleic, Nitric.  Removes dentinal smear layer: o Exposes collagen fibrils.  Simultaneous enamel etch.  Rinse: o Keep moist.

-

Primer:  Bifunctional monomer: o Link:  Hydrophilic collagen.  Hydrophobic resin. o Example:  HEMA.

-

Adhesive Resin:  Unfilled or lightly-filled monomers: o Equivalent to enamel bonding. o Bis-GMA, UDMA, TEGDMA.  Stabilize the hybrid layer. o Fills up remaining pores.  Resin tags.  Links primer to composite resin.

-

Hybrid Layer:  Conditioner demineralizes dentin.  Inter-diffused with low-viscosity monomer: o Displaces water. o Bifunctional.  Resin mechanically interlocks collagen.

230

•

Etch & Rinse (Two-Step):  

•

Self-Etch (Two-Step):  

•

Combined conditioner and primer. Adhesive resin.

Self-Etch (one-Step): 

•

Conditioner. Combined primer and adhesive: o Higher technique sensitivity:  Higher solvent-to-monomer ratio.  Risk of applying too thin.  Apply multiple layers.

Combined: o Conditioner. o Primer. o Adhesive.

Resin-modified Glass-Ionomer: 



Two-step: o Weak conditioner. o Mix and apply glass Ionomer adhesive. Fluoride release.

 Matrix system: •

Palodent Sectional Matrix: 12345-

Darway, Incorporated. BiTine Ring and BiTine.ii Ring. Sectional matrix sizes. Standard matrix: 0.002inch. Mini-matrix: 0.0015inch. 231

•

Automatrix II System: 1- Single-use self contained units. 2- No retainer needed. 3- Transparent bands available.

 Wedging: •

Cure through reflective wedges:  

Reflect 90% of light at a 90° angle towards the proximal surface. Lateral reflecting wedges were superior to transparent non-reflecting wedges in inducing superior margins.

B- Post-Insertion Procedures: •

Finishing Procedures:    

•

12-B blade to remove interproximal gingival excess. Fine-diamond finishing strips. Aluminum Oxide finishing discs. Carbide finishing burs.

Recommended Finishing Procedure: -

STEP 1:  12-Fluted carbide burs: o 7406: occlusal anatomy. o 7901: marginal ridge, proximal embrasure. o 7801: refine occlusal anatomy.  Use these burs dry, low-end of high speed range with light touch.  Minimize cavo-surface margin contact.  Sof-flex discs: interproximal areas.

232

•

-

STEP 2:  Intermediate finishing: o Bonded elastic or rubber abrasives.  Enhance finishers: minimally abrasive to adjacent enamel.  Aluminum-oxide bonded abrasives: used dry with light to moderate pressure and air to clear the field and dissipate heat buildup.

-

STEP 3:  Aluminum oxide-containing composite polishing paste.  Prisma-gloss (Dentsply/Caulk) or Enamelize (Cosmedent).  Use Enhance polishing cups and dry/wet technique.  Proximal Areas: disc-shaped felt devices.  Super Snap Buff Disc (Shofu) or Flexibuff (Cosmedent)

Finishing Procedures:   

•

Raptor. Profin. Brasseler.

Polishing procedures: 

Use composite surface sealant.

233


Revision: 1- What is the C factor: a- It is the ratio of bonded to un-bonded walls. 2- High C factor includes: a- Higher polymerization shrinkage. 3- The type of composite that is more prone to surface discoloration is: a- Chemical Cured. 4- Surface discoloration is because of: a- Roughness. 5- Nano-filled composite is: a- Highly polishable. 6- The type of composite that has the feel of amalgam is: a- Packable composite. 7- Deep cavity composite is: a- Chemical cured 8- Instead of amalgam in medium & small cavities we can use: a- Resin Composite. 9- The amount of filler in hybrid composite is: a- 35% by weight, 50% by volume. 10- CSA of composite is: a- 135°. 11- An instrument used with composite: a- Teflon. 12- We use which type of matrix with composite? a- Mylar clear.

234

13- Composites with filler particles: a- Macrofilled. 14- When high occlusal stresses and esthetic is of prime concern, we use: a- Hybrid composite.

235


Student Notes:

236

237

Chapter 7: Cavity Preparations for Dental Composite:

238

Class I Composite
Objectives: 12345678-

Be acquainted of different designs of class I cavity preparation. Know the difference between simple, compound and complex class I cavity. Be able to list and identify different outline forms. Know the proper resistance forms of composite resin cavities. Compare between different conservative cavities and conventional cavity. Identify the proper retentive features used in class I cavity for composite resin. List and explain why we do toilet to the cavity and how to check it. Know, list and explain how gaining access is done using a suitable sized #330 bur high speed or #245 conventional speed; the direction of cutting is parallel to the long axis of the tooth until reaching the dentin. The cutting is done through the weakest portion of the tooth, i.e. central or proximal triangular fossa. 9- Know, list and explain how lateral extension of the cavity to include all pits and fissures. Proximally; the extension is done midway between the marginal ridge and the proximal triangular fossa. Buccally and lingually, the extension should not exceed the ¼ inter-cuspal distance. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 10- Know, list and explain how finishing of cavity walls and margins is performed cylindrical fissure bur. The bucco-lingual dimension of the cavity should be ¼ the inter-cuspal distance, while the depth of the cavity should be from 0.5 mm beyond the DEJ. 11- The directions of the buccal and lingual walls of the finished cavity should be parallel occlusally, while the distal and mesial walls should be diverging occlusally. The cavo-surface angle of the finished cavity should be 90° or short bevel. 12- Describe the technique of insertion of composite resin restoration 13- Recognize the problem with neglecting to do beveling of cavity walls.

239

Class I Composite
Definitions:  Class I lesion: Pit and fissure caries.  Class I composite: Pit and fissure caries restored with composite restoration.


Indications:    

Esthetic is a prime concern. Occlusion is favorable. Oral hygiene is good. Small to moderate size lesion.


Contraindications:    

The operating site cannot be isolated. Heavy occlusal stresses. Bad oral hygiene. Large size lesion.


Advantages:       

Esthetic. Conservation of tooth structure. Reinforce weakened tooth structure. Can be re-bonded. Eliminate galvanic current. Eliminate mercury toxicity. Low thermal conductivity.

240


Disadvantages:   

Low wear resistance. Polymerization shrinkage. Technique sensitive.


Shade selection: 

 

Determine the shade before: o Teeth are subjected to any prolonged drying. o Rubber dam application. Most manufacturers provide shade guide for their specific materials. Good lighting, either natural or artificial, is necessary when the color selection is made.


Class I composite resin: 

When restoring the occlusal surface of a posterior tooth there are three possibilities: o Occlusal sealant. o Preventative resin restoration (PRR). o Tradition class I restoration.


Class I preparation:    

Conservative follows outline of decay. 0.5 mm into dentin (or deeper). No occlusal bevel. Rounded internal line angles best.

241


Class I preparation/restoration:        

Decay present to DEJ or beyond. Traditional preparation done. Base/liner placed if deep. Enamel and dentin acid etched. Primer/bond resin placed, dried, cured. Composite resin placed, cured. Occlusal adjustment done. Restoration finished.


Class I Cavity preparation: 



Pulpal protection: o Calcium hydroxide. o RM-GIC . Acid etching: o Start applying the etchant to enamel margins then into dentin. o Rinse and wash with water, leave the tooth moist.


Class I:  Primer: Apply primer then air dry.  Adhesive:   

Apply adhesive then use a brush to thin it. Don’t air thin it. Light cure.

 place composite:  

Incremental placement. Horizontal or vertical increment Hori.

242


Rebonding:   

Rebonding: the application of a low-viscosity resin called “surface sealers” to the finished surface and margins of a restoration. Finishing and polishing procedures are inherently destructive to the restoration surface. Finishing can exacerbate the marginal gaps formed during polymerization.

 Rebonding has been shown to:    

Improve the marginal integrity of composite resin. Reduce micro-leakage. Reduce marginal staining. Reduce wear.

 Technique:   

Apply etchant to the marginal areas for 10 seconds then rinse and dry. Apply rebonding resin then thin with a brush. Light cure for 20-40 seconds.


Class I restoration:       

Acid etch enamel and dentin. Rinse well (5 – 10 seconds). Apply primer/bond to moist dentin. Dry and cure (10 – 20 seconds). Place C.R. and cure (40 seconds). Check occlusion, adjust. Finish.

243


Student Notes:

244

245

Class V Composite
Objectives: 1234567-

Be acquainted of different designs of class V cavity preparation. Know the difference between simple, compound and complex class V cavity. Be able to list and identify different outline forms. Compare between different conservative forms of cavities. Identify the proper retentive features used in class V cavity for composite resin rest. Explain of the no need of convenience form in class V. Be able to identify and differentiate between the proper, correct and incorrect cavity walls and margins locations and what were the causes of differences. 8- List and know the different location of the gingival walls and we need to bevel it. 9- Explain the need for bevel the occlusal wall and which type of bevel considered the most proper. 10- List and explain why we do toilet to the cavity and how to check it. 11- Know, list and explain how gaining access is done using a suitable sized #330 bur high speed or #245 conventional speed; the direction of cutting is perpendicular to the long axis of the tooth until reaching the dentin from the lingual side. 12- Know, list and explain how lateral extension of the cavity is done proximally. Occlusally and gingivally, the extension should not exceed the high of contour and one mm over the cervical line. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 13- Know, list and explain how finishing of cavity walls and margins is performed. The depth of the cavity (axial wall) should be from 0.5 mm beyond the DEJ and the axial wall should be convex mesio-distally. 14- The directions of the occlusal and gingival walls of the finished cavity should be parallel to the occlusal plane, while the distal and mesial walls should be diverging proximally. The cavosurface angle of the finished cavity is a short bevel. 15- Describe the technique of insertion of composite resin restoration. 16- Recognize the problem with neglecting to do beveling of cavity walls.

246

Class V Composite
Definition: Cavity located in the gingival 1/3 of facial & lingual surface of all teeth.


Indications: 1- Caries is the most clear cut indication. 2- Root caries in older patients with: a- Low salivary flow. b- High sucrose intake. c- After head & neck radiation. d- Gum retraction. 3- Cervical erosion/abrasion:


Treatment is indicated in: 1234-

Caries. Sensitivity. If the lesion is esthetically objectionable. If notched defect.


Etiology of these lesions: 1- Abrasion: 

Wearing or loss of tooth structure due to mechanical forces as: a- Tooth brushing with hard bristle tooth brush. b- Abrasive tooth paste (is V shaped).

2- Erosion: 

Due to sustained exposure to citric acid (juices or vomitus).

247

3- Idiopathic: 

Due to flexure of the cervical area under heavy occlusal stresses. This process is called Abfraction.


Selection of the restoration: A- Amalgam: 1- In areas esthetic is not a concern. 2- When mechanical retention can easily be obtained. 3- Patients with low caries index.

B- Glass Ionomer: 

In patients with high caries index.

C- Composite: 

When esthetic is of prime importance and maybe used with or without glass Ionomer (sandwich technique): a- Is the most esthetic restorative material. b- Has good wear resistance and longevity.


Contraindication: 

Sometimes it is contraindicated in elderly patients on the root surface due to: 1- Decreased salivary function. 2- Decreased ability for homecare. 3- Difficult to isolate the operating area.

248


Before cavity preparation: 1- Select the shade guide. 2- Isolation using rubber dam and No. 212 retainer, for: a- Visibility. b- Retraction of gingival tissues. c- Moisture control very important for tooth colored restoration. 3- Micro-filled composite often used for: a- High polishability. b- Restoration flexibility when the tooth under goes cervical flexure.


Cavity preparation: 

Determined by many factors: o Kind of lesion. o Depth. o Size. o Location. o Sub-gingival or supra-gingival.


Types of class V cavity preparations: 1- Conventional class V cavity preparation: •

Indications: 

Lesions that extend into the root surface, no enamel on all margins of the preparation.

249

•

Cavity preparation: 1- Cavo surface margin is 90°. 2- Axial depth is 0.75mm, this provides adequate external wall width for: a- Strength of cavity walls. b- Strength of composite. c- Placement of retentive grooves. 3- Lesion is entirely in root surface. 4- Axial walls are convex. 5- Remaining infected dentin excavated and liner is placed. 6- Inciso-axial &gingivo-axial grooves prepared.

2- Beveled conventional class V cavity preparation: •

Indications: 

•

Groove retention: 

•

A large new carious lesion that has a part in enamel incisally (occlusally), possibly mesial & distal margin in enamel as well, and the cervical part will have gingival retention groove. o Many of these preparations will be a combination of beveled enamel margin (incisally) and 90° root surface (non-enamel margin) with root surface has groove retention. o Combined bevel conventional & conventional preparation

Is not indicated when the peripheries of the cavity preparation is located in enamel.

Advantages of beveled conventional cavity preparation: 1- Increased retention due to the greater surface area of etched enamel afforded by the bevel. 2- Decreased micro-leakage due to enhanced bond between the material & the tooth. 3- Decreased need for groove retention form and consequently less removal of tooth structure.

250

•

A gingivo-axial groove is indicated in the root surface because: a- Adhesion to cementum & dentin is not as reliable as adhesion to enamel. b- Because polymerization shrinkage of composite tends to adhere to the enamel margins but pulls away from the dentin or cementum on gingival margin. c- Resist tooth flexure.

•

When large class V carious lesion is extended into the root surface:    

•

The gingival wall is prepared in the same manner as conventional. Butt joint with retentive groove. The depth is 0.75mm on the root surface. Only bevel the enamel cavo surface margin.

Cavity preparation:    

  

Prepare outline form before expect the depth is only 0.2mm. in dentin when groove is unnecessary. Remove any infected dentine. Apply Ca(OH) liner or base. Prepare gingival groove if: 1- The gingival margin is located on root surface. 2- If the preparation is large enough to warrant groove retention form. Enamel margin is beveled using coarse flam shaped diamond instruments angled 45° to external tooth surface and prepared to width 0.25mm to 0.5mm. When decalcified area extend mesially from cavitated class V lesion. A completed beveled conventional class V and prepare a conservation mesial extension by round diamond instrument in enamel only.

3- Modified class V cavity preparation: •

Indications: 

Small enamel defect or small cavitated lesion that is largely or entirely in enamel. These include decalcified & hypoplastic areas located in the cervical third. The objective is to restore the defect or lesion as conservatively as possible.

251

•

Cavity preparation: 1- Prepare initial cavity preparation with round or elliptical diamond instrument eliminating the enamel lesion or defect. 2- No groove retention will be used. 3- No effort is made to prepare 90° cavo-surface margin. 4- The infected dentin is removed if present with round bur. 5- Apply calcium hydroxide but only if indicated. 6- Then make etching of enamel.

4- Class V cavity preparation for abrasion/erosion: 1- Roughening the internal cavity walls. 2- Placing retentive grooves in non-enamel areas. 3- If necessary prepare the root surface cavo surface margin to approximately 90°.


Finishing:    

Removal of excessive composite by finishing bur. Aluminum oxide disk (softless disk). Fair diamond bur. White stone/rubber cup with polishing paste.

252

Note: We use the transparent cervical matrix for contouring, smoothening & polishing the surface.


Revision: 1- Class V upper 6 should be: a- Convex or flat or concave. 2- The best type of restoration used in class V is: a- Microfilled.

253


Student Notes:

254

255

Class II Composite
Objectives: 123456789-

Be acquainted of different designs of class II cavity preparation. Know the difference between simple, compound and complex class II cavity. Know and identify the different component parts of compound class II cavity. Be able to list and identify different outline forms. Know the proper resistance forms for class II cavity preparation. Compare between different conservative cavities. Identify the proper retentive features used in class II cavity for composite resin rest. Explain when the convenience form in compound class II cavity for composite is needed. Be able to identify and differentiate between the proper, correct and incorrect cavity walls and margins and what were the causes of differences between ( the uniform, straight and reverse curve ) buccal wall extension. 10- List and explain why we do toilet to the cavity and how to check it. 11- Know, list and explain how gaining access is done using a suitable sized #330 bur high speed; the direction of cutting is parallel to the long axis of the tooth until reaching the dentin. The cutting is done through the weakest portion of the tooth, i.e. central or proximal triangular fossa. 12- Know, list and explain how lateral extension of the cavity to include all pits and fissures is done using the 330 bur, and the proximal cavity will be created buccally, lingually and gingivally. The extension should not exceed the ¼ inter-cuspal distance. The cutting is performed through the dentin upward to remove enamel, which becomes undermined. 13- Know, list and explain how finishing of cavity walls and margins is performed using #330 bur. The facio-lingual dimension of the cavity should be ¼ the inter-cuspal distance, while the depth of the cavity should be from 0.5 mm beyond the DEJ. And understand the difference width of gingival floor for premolar and molar and when the proximal contact is need to be open or not. 14- The directions of the facial and lingual walls of the finished cavity should be parallel. Axial wall should be convex facio-lingual. The cavo-surface angle of the finished cavity should be a short bevel. 15- Describe the technique of insertion of composite resin restoration. 16- Recognize the problem with neglecting to do beveling of cavity walls.

256

Class II Composite
Diagnosing class II caries: A- Manuel way, by using: 1- Bitewing film – posterior teeth. Periapical film – anterior teeth. 2- Transmission. 3- Dental floss. 4- Explorer instrument. 5- Caries detector.

B- Digital way, by using RPG, by analyzing the density of Ca in the normal & affected dentin.


Preparation & Restoration: 1234-

Proximal surfaces of posterior teeth. Similar to class II amalgam restoration. Prepared with same burs/diamonds as amalgam. No cavo-surface bevel except non stress bearing areas.


Class II preparation comparison: Amalgam

Composite

0.5 to 1 mm into dentin.

0.5 mm into dentin.

No cavo-surface bevel.

Cavo-surface bevel buccal and lingual of proximal.

Contact 0.5 mm proximal clearance.

Contact can be left.

Isthmus 1/3 between cusps.

Isthmus according to caries.

No gingival bevel.

No gingival bevel.

Occlusal dovetail.

Dovetail if needed.

N.B. bevel is placed to enhance resin composite adaptation and seal

257


Class II composite preparation:        

Check occlusion – Articulating paper. Outline form – Conservative. Retention/resistance – Acid etch. Convenience form – Finishing restoration. Removal of caries – Non-calcified dentin. Pulp protection – Resin modifies GI. Finish of margins. Cavity cleansing – Air-water spray.


Bur selection:    

#330 – Pedo bur. #245. #170. #169.

258


Student Notes:

259

260

Class III Composite
Objectives: 12345678-

Be acquainted of different designs of class III cavity preparation. Know the difference between simple, compound and complex class III cavity. Be able to list and identify different outline forms. Know the proper esthetic forms of composite resin cavities of class III. Compare between different conservative cavities. Identify the proper retentive features used in class III cavity for composite resin. List and explain why we do toilet to the cavity and how to check it. Know, list and explain how gaining access is done using a suitable sized #330 bur high speed or #245 conventional speed; the direction of cutting is perpendicular to the long axis of the tooth until reaching the dentin from the lingual side. The cutting is done through the weakest portion of the tooth. 9- Know, list and explain how lateral extension of the cavity to include the entire lesion. Proximally; the extension is done inciso-gingivally the cutting is performed through the dentin upward downward to create semi-lunar in shape on the lingual surface involving no more than one half of the width of marginal ridge. 10- Know, list and explain how facial tooth structure should be preserved. Do not cut the preparation clear through the proximal contact. 11- Recognize to develop a definite outline which is bowl-shaped when viewed from the proximal. 12- Explain how adequate retention is gained with a gingival groove and incisal cove and a slight bevel is placed along the entire periphery of the cavo-surface margin. 13- Describe the technique of insertion of composite resin restoration. 14- Recognize the problem with neglecting to do beveling of cavity walls.

261

Class III Composite
Definition: Lesions initiating in proximal surface of all anterior teeth, not involving incisal angle.


Class III for composites: Difficulty of preparation of class III due to: 1- Adjacent tooth. 2- Limited space. 3- Need of good esthetic. 4- Difficulty of gaining access.


Advantages of lingual approach: 1234-

Conservation of facial enamel. Better esthetics. Discoloration of composite less visible. Possibility of leaving unsupported labial enamel.


Indications of facial approach: 1234-

Lesion positioned facially. Irregular alignment of teeth. Extensive caries labial. Replacement of faulty restoration placed form labial.


Direct access by proximal when: 1- Existing cavity in neighboring tooth. 2- Wide interproximal space (diastema) or missing neighboring tooth. 3- Neighboring tooth has temporary cemented crown.

262


Preparation lingual access: 1- Unless absolutely necessary, don’t include:  Proximal contact.  Facial surface.  Sub-gingivally. 2- Axial depth is 0.75 mm to 1.25 mm. 3- Axial wall convex. 4- Beveling of enamel margin. 5- Width of bevel from 0.25 to 0.5 mm.

 Bevel may be cut only on lingual in case of: 

Beveling facial margin exposing dentin damaging esthetic.

 Not recommended in lingual in: 

Areas of centric contact subjected to heavy forces.

Note: Advantages of beveling enamel margin: 1- Increase surface area >> increase retention. 2- Flushing composite with tooth >> better esthetic. 3- Proper bonding >> reduce micro leakage. 4- Prevent bulging of composite >> prevent appearance of line of demarcation between tooth & composite.


Facial access: The same as lingual access but more simplified because: 1- Direct vision. 2- The lesion usually larger.


Types of Class III: A- Conventional Class III Root surface caries: Cavity is rarely completely in the root surface but mainly it has a portion in the root surface and a part in the crown.

263

•

The root surface portion: 1- Cavo-surface angle is 90° (butt joint). 2- Walls perpendicular to root surface. 3- Depth is 0.75 mm in dentin: A- For bulk of restoration. B- Placement of groove. 4- Groove retention (axio-cervical & axio-incisal grooves) is necessary ( no enamel ) to: A- Increase retention. B- Optimize the seal of the material. 5- No bevel.

•

The crown part: Enamel margin is present: 1- Beveled margins. 2- Pulpal depth according to the caries. 3- Retention by acid etching.

B- Beveled Conventional Class III:   

For replacing defective existing restoration in the crown portion of the tooth. Restoring large carious lesions. In this case I can’t put the composite directly in the deep cavity because it’s irritant, so I have to: 1- Protect the pulp by placing Glass Ionomer below the composite (sandwich technique). 2- Acid etch by using 35% of phosphoric acid (gel or solution) or 10% maleic acid in the enamel & GI. 3- Use bonding agent. N.B. the matrix that is used in composite is the plastic matrix.

C- Modified Class III:    

Indicated for small and moderate lesions or faults. Is usually removed from lingual approach. Must be as conservative as possible according to the extension of caries. No groove or cove is indicated.

264


Revision: 1- If class III is extended gingivally to the root, it is: a- Better to use butt joint. 2- The main way of retention in class III is: a- Micromechanical. 3- A mylar strip in class 3 is placed: a- To retract the gingiva. 4- In class 3 lingual approach we should: a- Reserve labial enamel. 5- Means of retention in class 3 root caries: a- Axio-gingival groove (micromechanical).

265


Student Notes:

266

267

Class IV Composite
Objectives: 1- Be acquainted that the preparation will stimulate dealing with a fracture anterior tooth as well as the situation where a large class II lesion has progressed to include loss of incisal angle. 2- Know how to avoid undermining and weakening of incisal angle in large class III. 3- Be able to list and identify different outline forms. 4- Know the proper esthetic forms of composite resin of class IV. 5- Compare between different conservative cavities. 6- Identify the proper retentive features used in class IV cavity for composite resin by skirting bevel all over the fracture angle and that the retention will be through micro-mechanical retentive mean. 7- Describe the technique of insertion of composite resin restoration. 8- Recognize the problem with neglecting to do beveling.

268

Class IV Composite
Definition: Caries in the proximal surface of anterior teeth involving incisal angle.


Indications: 1- Fracture of incisal angle (trauma, accident). 2- Caries that destroy or severely weaken incisal angle. 3- To replace an existing restoration.

 Fractured incisal angle may involve: 1- Enamel only. 2- Enamel and dentin without pulp involvement. 3- Enamel and dentin with pulp involvement.

 If caries are present: X-ray is helpful to see: 1- The extension of carious lesion. 2- The proximity to the pulp.


For fractured incisal angle: 

Bevel is the only preparation

269


Types of bevels: 1- Short bevel (partial bevel): Involve 1/3 to ½ of enamel wall. 2- Long bevel: Entire enamel is beveled at 45 degree to 75 degree by flame shape bur. 3- Full bevel: Enamel and dentine are beveled (full wall length). 4- Hollow ground bevel: About 2/3 of enamel thickness is ground in concave manner by round bur.

5- Scalloped: May be used with short or long bevel to increase surface area for bonding. 6- Skirting (mini chamfer): When enamel is the main retentive feature for the restoration.


Advantages of bevel: 1234-

Increase surface area. Increase retention. Reduce marginal leakage. Better esthetic.


Technique:  

Clean the tooth with pumice and water. Select shade guide before rubber dame placement.


Anesthesia:   

Not necessary for small fracture limited to enamel. Large fracture needs anesthesia as exposed dentin become sensitive to heat, cold or air. Place rubber dam.

270


Preparation:  Design 1: 

Chamfer 1mm long or half the length of the fracture and half the depth of enamel on labial and lingual surface.

 Design2:   

3mm bevel in place of chamfer. The bevel is more esthetic but liable chipping. If the original fragment is available after fracture may be reattached to the tooth by etching and bonding.


Use of pins:   

No need for retentive pins for composite restorations. Adhesive technique provides sufficient retention. The use of pins leads to: o Color change of the composite. o Corrosion discoloration. o Recurrent caries.


Composite restoration:    

Protect adjacent tooth with Mylar strips. Acid etching for 15 seconds. Washing and drying. Application of bonding agent and light cure.

271


Composite placement: 1- Using clear plastic strip and wedge. 2- Using clear plastic crown.   •

First technique:   

•

It may be filled with composite and placed over the preparation and wedged in place. Excess material is removed with explorer or inter-proximal carvers. Light curing for 60 seconds for facial and 60 seconds for lingual.

Second technique: 

•

The crown form should be trimmed to cover 1mm above the margins of the preparation. In case tied contact pre wedging must be done.

Use only the lingual and proximal part of the crown form leaving the labial aspect open for incremental building of composite for better esthetic.

Third technique (over-lay technique): 

The bulk of the restoration is built with hybrid composite to provide strength and the final layer is veneer of micro-filled composite for smooth and glossy appearance.

272

3- Layering technique: •

Technique: 123456789-

•

Anesthesia. Long bevel 2-3mm according size of fracture. Alginate impression poured in stone model. Waxing up to the desired shape. Putty matrix fabricated overt the wax up. Accurate shade guide before tooth could dehydrate. Etching and bonding. Building composite in layering technique. Finishing and polishing.

Layering sequence: 12345-

Lingual shell. Dentin layer. Translucent layer. Opaque layer. First enamel layer.


finishing of composite: 1- Aluminum oxide disc. 2- Sand paper disc. 3- Metal disc


For carious class IV:  

Caries and weak tooth structure is removed. Bevel is created on facial surface.

273


Revision: 1- in Class IV tooth 11 we put the mylar strip between: a- The tooth and the wedge. 2- Advantages of Skirting: a- Esthetic and more retention. 3- Function of beveling: a- Expose the dentinal tubules. 4- Hollow Ground Bevel: a- 2/3 of enamel thickness is ground concave. 5- Clear (celluloid crown) is indicated in: a- Class IV restorations.

274


Student Notes:

275

276

Chapter 8: Pit & Fissure Sealants and Preventive Resin Restorations
Objectives: By the end of this lecture, the student should: 1- List treatment Options for pits and fissure decay sequentially (starting with monitoring and ending with restorations for frank cavitations). 2- Explain what are the objectives of placing sealants. 3- Describe the anatomy of pits and fissures and explain difficulties of cleaning and sealing such areas. 4- Identify reasons behind limited used of sealants. 5- Give reasons of dentists’ hesitations and reluctance to use sealants. 6- List indications of using sealants and identify situations when presented with clinical cases. 7- Discuss sealants effectiveness regarding caries prevention citing a minimum of 3 studies. 8- List factors affecting retention rates of sealants. 9- Explain possibility of placing sealants by auxiliary staff. 10- Discuss cost-effectiveness of using sealants in populations with different caries status. 11- List and compare different ways of cleaning teeth before placing sealants. 12- List different approaches for preparing teeth for sealants placement (e.g. Air abrasion, Enameloplasty). 13- Compare ways of preparing the teeth for sealant placement and identify the best approach. 14- Explain the technique of Enameloplasty and whether or not it should be a routine approach. 15- Describe effect of topical fluoride on sealants. 16- Name the types of acids used for acid-etching of enamel, its percentage, and clinical significance of using different types. The student should also identify different forms of acids (liquid or gel), and clinical implications of using either type. 17- Recall the appropriate duration of etching for primary and permanent teeth. 18- List types of sealants (resin-based, GIC, filled or not, opaque etc). 19- Identify components of resin-based sealants. 20- Discuss possibility of harmful effects of sealants due to estrogenicity issue (Olea work and later work). 21- Recognize problems with GIC sealants. 22- Explain clinical implications of using filled and unfilled sealants. 23- List advantages and disadvantages of using colored and clear sealants. 24- Discuss the use of fluoride in sealants. 25- Discuss the use of intermediate bonding layer and its advantages and disadvantages. 26- Name at least one new development of sealants. 27- Sequentially describe the technique of placing the sealant. 28- Identify reasons for sealants loss and explain how to avoid them. 29- Explain what is PRR and what types of restoration is used in different clinical situations. 30- List advantages of PRR, indications and contraindications. 31- Explain the steps of PRR, identifying the equipment died restorations needed. 277

Pit & Fissure Sealants
Introduction: Traditional caries management has consisted of detection of caries lesion followed by immediate restoration. In other words, caries was managed primarily by restorative dentistry. However, when the dentist takes the bur in hand, an irreversible process begins. Because this is the start of a restoration cycle in which the restoration will be replaced several times. Therefore, before restoration, a group of certain questions has to be asked:  Is the caries present?  If so how far does it extend?  Is the restoration required or could the process be arrested by preventive treatment? o The modern dentistry & with the introduction of adhesive dentistry, the dentists are allowed to seal the susceptible areas & make smaller preparations. Thus preserving hard dental tissues.


Definitions:  Pit and fissure sealant: Is a thin plastic coating placed in the pit and fissures of the teeth to act as a physical barrier to decay.

 Preventive resin restoration: If additional preparation is needed to the pits and fissures other than opening of the fissure, flowable resin composite is placed in that area & remaining fissures and surface of resin composite restoration is sealed with a sealant material.

278


Rationale:  Why fissures are caries susceptible? Pits & fissures provide a sheltered environment in which dental plaque can develop so that these areas are liable to decay.  Almost over 85% of children (5-17 years old) have caries in the pits and fissures.  Since it is difficult to diagnose decay “demineralization” in its early stages & fissures are susceptible sites, the dentist may decide to fissure seal susceptible teeth as soon after eruption as possible.  Fluoride is least effective on pit and fissures.  15 year study – 68% of sealed teeth were caries free vs. 17% of unsealed control group.


Indications:  Pit and fissure sealants: When active fissure caries has been diagnosed or if a high risk has been established and fissures have susceptible morphologic characteristics, sealants are indicated.  Deep fissures.  Incomplete or ill formed pits.  Newly erupted teeth.  High caries rate.  Children.  Molars.

 Incipient Caries: Incipient Caries Studies have shown that sealants can be placed over incipient caries which arrests the caries process. Most dentists choose to use air abrasion, a bur, or a laser to remove the caries before the sealant is placed.

279


Contraindications:      

Shallow fissures. Well coalesced pits. Fluoride rich enamel. Low caries rate. Occlusal or proximal caries. Adults.


Types of sealants:  According to composition: •

Resin sealants:  

•

(Bis-GMA) Bisphenol A-glycidyl methacrylate resins. Urethane-based resin.

Types of reactions: Resin Sealants – Polymerization reaction. G.I. Sealants – Acid-base reaction.

Glass Ionomer sealants:     

Aluminosilicate glass & polyalkenoic acid. Anticariogenic. More viscous. Less retention (6-12m). Less resistant to occlusal wear.

 According to curing mechanism: •

Chemical cured sealants:  

“autopolymerization” Composed of: o Base and catalyst. o Monomer & Initiator +Diluted monomer &5% Organic Amine accelerator = Sealant.

280

•

Visible light cured sealants:  

“photopolymerization” Composed of: o Pre-mixed Dimethacrylate + Diluent + Activator + Light = Sealant.

 Chemical cure sealant materials: •

Advantages:  

•

No cure light or risk of eye damage. Can apply sealants to several teeth.

Disadvantages:   

Variation in setting time (appx. 2 min). Voids from mixing material. Changes in viscosity over time.

 Light cured sealant materials: •

Advantages:    

•

Short setting time (appx. 20 seconds). No mixing required. Longer working time. Does not get thick.

Disadvantages:    

Potential eye damage due to light cure. Additional cost of curing light unit. Cure time increased with number of teeth sealed. Difficult to manipulate cure light for more posterior teeth.

281

 According to shade:   

Clear. Tinted. Opaque.

•

Clear sealant: 

•

Tinted or Opaque sealant: 

•

Has the advantage of being able to see the tooth beneath it to detect any color change that may indicate leakage and development of a carious lesion.

Has the advantage of being able to see the partial loss of the sealant and then the sealant may be repaired.

Recently: 

Clinpro™ Sealant goes on pink for easy-tosee application, and cures to a natural white.

 According to fluoride release:  

Fluoride-releasing sealant. Non-fluoride containing sealants.

 According to filler content:  

Filled sealants. Unfilled sealants.

•

Unfilled sealants:  

They are less viscous and better able to penetrate into fissures than filled sealants. Consequently: o Tend to be better retained. 282

o Suffer less leakage. o Offer rapid loss of any occlusal interference.

 Strength and Viscosity Characteristics Viscosity: •

Viscosity: 

•

The thicker the sealant the less likely to penetrate to depth of fissure.

Wear of Sealants: 

Considerations for wear – less filler, more wear and vice versa.


Selection of cases:  Considerations:       

Patient age. Oral hygiene. Caries risk. Diet. Fluoride history. Tooth type. Morphology.


Manipulation:  Sealant Kits:    

Cavity Indicators. Drying agent (optional). Acid etch. Sealant material.

 Prepare the tooth: •

For sealants: 

Bristle brush or rubber cup and plain pumice or prophy jet.

283

  •

Sharp explorer to clean out debris. Rinse.

For PRR: Preparation of the fissure by the use of:   

Air abrasion. Bur. Laser.

 Check occlusion: 

Avoid placing acid etch and sealant on marked areas from articulator paper.

 Isolate tooth/teeth: N.B. Treat quadrants separately. WHY? In order to control isolation, THUS preventing contamination by moisture.

 Apply acid etch:      

15-20 seconds. Use blue micro tip or brush tip. Apply only in pit and fissures. For liquid – dab but do not rub. Re-etch 10 seconds if there is any saliva contamination. N.B. Etch longer in the following cases: o Deciduous teeth. o Saliva contamination. o Air abrasion or prophy jet used. o Highly mineralized teeth.

 Rinse tooth/teeth:    

Use HVE and A/W syringe. Proper – usually 10-20 seconds rinse. Avoid saliva contamination. Re-isolate.

284

NOTE: DO NOT use explorer after etching.

 Dry tooth/teeth:  

Should appear chalky or frosty white if etched. If not, re-etch for another 10 seconds if not contaminated with saliva.

 Drying agent (PrimaDry):  

Acid etching and Primadry (alcohol based) allows enamel to be easily “wetted”. Active ingredient of Primadry is ethyl alcohol.

 Apply drying agent (PrimaDry):    

Use brush tip. Apply and leave for 5 seconds. Gently blow air to dry. DON’T RINSE.

 Apply sealant material:     

Most posterior tooth first. Extend 1 - 2mm beyond pit and fissures. Gently work into pits and fissures. Don’t overfill. “Pop” bubbles in sealant with explorer or brush tip before curing.

 Light cure for 20 seconds:   

20 seconds each tooth. Avoid touching sealant material with the tip of the light cure. Don’t let saliva contaminate the field. N.B. sealant will appear shiny/wet.

 Light cure for 20 seconds – air inhibition theory:  

Top layer of sealant will remain uncured. Sealant will appear shiny / wet.

 Check sealed teeth: 

Use explorer. 285

 

Tooth should be smooth but not soft. Re-apply sealant, if necessary. (Remove uncured sealant with wet cotton roll).

 Check occlusion:   

Articulating paper. Ask patient how it feels. Dentist can adjust with bullet-shaped finishing bur or polishing stone. N.B. If using unfilled composite sealant the bite will self-adjust in 2-3 days.


Failure & Repair:  Retention of Sealants – 2 year study: •

Fluoride releasing sealant:  

>90% retention. No caries.

 Retention of Sealants – 4 year study: •

Fluoride releasing sealant:  

•

91% retention (77% complete & 14% partial). 10% caries rate.

Non-Fluoride releasing sealant:  

95% retention (89% complete & 6% partial). 10% caries rate.

 Sealing over caries: •

For incipient caries: 

The risk of progression is very small.

286

 Causes of sealant failure:   

Debris and/or saliva contamination. Air inclusion during manipulation – voids-surface voids which can discolor and retain plaque. Manipulating self-cured sealants late in the setting reaction-can disrupt polymerization and induce bond failure.

 Loss of Sealant:   

A contaminated site from faulty technique will likely result in complete or partial loss of the sealant within 6-12 months. Early loss means less retention of the resin. The main cause is moisture contamination.

 Clinical manifestation of sealant’s failure:   

Loss of all or part of the sealant. Staining at edges. Discoloration underneath sealant.

 Repair of sealant: •

If totally lost: Reapply.

•

If partial loss: Repair.   

Roughen with diamond stone. Re-etch 20 seconds. Reapply sealant.

287


Preventive measures:  Preventive Programs as Related to Sealants:    

Tooth brushing and flossing - mechanical plaque removal. Fluoride – chemical prevention. Dental visits – mechanical plaque removal and chemical prevention. Diet: o Minimize exposure to cariogenic foods and liquids that have little or no nutritional value. o Minimize solid and sticky foods. o Minimize slowly dissolving foods.

288


Student Notes:

289

290

‫ﺗﻢ ﺑﺤﻤﺪ ﷲ‬ ‫ﻻ ﺗﻨﺴﻮﻧﺎ من دﻋﺎﺋﻜﻢ‬ ‫ﻭﷲ اﻟﻤﻮﻓﻖ‬

‫‪291‬‬