Lec
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- Words: 2,086
- Pages: 41
10/14/08
1
Advantages of resin composites 1- Superior esthetics; They have refractive index close to that of enamel and dentin combined. The compositional filler scatters the incident light producing excellent depth of translucency. They are available in all possible toothcolors. 10/14/08
2
Advantages of resin composites 2- Composites have low thermal conductivity and diffusivity. Therefore, they do not transmit thermal shocks to underlying dentin and pulp. 3- Satisfactory physical and mechanical properties; that are considered to be satisfactory for clinical applications. 4- Easy to repair. 5- Strengthening of the remaining tooth structure via bonding system. 6- Conservation of tooth structures. 10/14/08
3
Disadvantages of resin composites
10/14/08
1- Questionable adaptation a- High polymerization shrinkage. Composite resin exhibits a clinically polymerization shrinkage of about 1.5-3 vol%, that causes the maturing resin to pull off substrate enamel and dentin surfaces, with tensile stresses of 17-20 MPa. The shrinkage gaps invite leakage with ingress of oral environmental bacteria, fluids, and stains causing acute clinical problems of dentin hypersensitivity, adverse pulp reactions, and recurrent caries. It is for this purpose that adhesive systems are used. 4
Disadvantages of resin composites
B- Poor wettability It has low wettability, due to material high viscosity and surface tension. This inhibits the spontaneous flow of the material, and diffusibility into substrate enamel surface ( with low surface energy) and substrate dentin surface ( with low surface energy). Moreover, the material is hydrophobic, and therefore is easily displaced off substrate surface by compositional water. Therefore, effective adhesive systems must be used to promote resin wettability of substrate surface.
10/14/08
5
Be aware
Sufficient wetting of the adhesive will only occur if its surface tension is less than the surface-free energy of adherend ( substrate tooth substance ). High surface energy of adherend -----» able to attract the atoms of adhesive. Low surface tension and low viscosity of adhesive ----» able to properly wet the adherend.
10/14/08
6
Disadvantages of resin composites
C- High differential coefficient of thermal expansion Composites have higher coefficient of thermal expansion than that of the tooth. The closer the coefficient of thermal expansion of the material is to that of enamel, the less chance for creating opening at the junction of the material and the tooth when temperature changes occurs. Bonding a composite to etched tooth structure reduces the negative effects of a difference between coefficient of thermal expansion of the tooth structure and the material.
10/14/08
7
Disadvantages of resin composites 2- Low wear resistance; It leads to: Opening of interproximal contacts. Loss of anatomic form and of vertical dimension. Makes the restoration vulnerable to surface degradation by environmental fluids, food chewing and plaque bacterial metabolic activities.
10/14/08
8
Disadvantages of resin composites
3- Hydrolytic instability. Resin-based restorations are subjected in the mouth to time-dependent structural, interfacial, and surface deterioration by complex mechanisms of hydrolysis ( by environmental acids ), water sorption ( in oral environmental fluid ) and marginal percolation with progressive deterioration of marginal adaptation, wear and loss of strength.
10/14/08
9
Disadvantages of resin composites
10/14/08
4- Potentials for adverse pulp reactions. Adverse pulp reactions are more frequent under composite restorations. They were believed to be due to residual compositional constituents of composite resin. Recent researches have confirmed their bacterial etiology.
10
Disadvantages of resin composites
5- Technique sensitivity. It has potentials to exhibit significant variations in properties, handling characteristic, and clinical performance in response to deviations from manufacturer instructions relative to details of substrate surfaces pre-treatment and application of composite.
10/14/08
11
Disadvantages of resin composites
6- Lack of cariostatic potentials. Anticariogenicity through incorporation of fluorides has not been successful with composite because its extremely low solubility prevents sustained release of sufficient amount of fluoride ions.
10/14/08
12
Indications
10/14/08
1- Carious defects: Class I and II cavities that can be isolated properly and where centric contact (s) on tooth structure is (are) present. Class III, IV and V.
13
Indications
10/14/08
2- Non-carious lesions: Hypoplasia. Hypocalcification that is esthetically objectionable or is cavitated. Abrasion and erosive lesions. Class VI cavities ( faulty pit on selected occlusal cusps ). Abfraction lesion, ( cervical induced cavities owing to the flexure of teeth during function as a result of the presence of an occlusal interference ). 14
Indications Non-carious lesions
Enamel hypoplasia Abfraction 10/14/08
15
Indications
10/14/08
2- Non-carious lesions: Veneer for metal restorations. Repair of fractured areas. Core build-up. Cementation of orthodontic brackets. Luting purposes. Splinting of mobile teeth. Restoration of a weakened tooth that can be strengthened by a bonded restorations. 16
Contraindications
10/14/08
When the occlusal contacts will be on the composite material. Heavy occlusal stresses due to unfavorable occlusion. Deep subgingival areas that are difficult to prepare or restore. Poor oral hygiene. Wherever provision of dry field is not possible. Bruxing patients. 17
Designs of cavity preparation: A- Modified cavity design:
The introduction of adhesive practice i.e. bonding to enamel and dentin, has modified the classic cavity preparation in to what is known as the adhesive or conservative cavity design. These cavities are characterized by: A- Minimum extensions. B- Beveled cavo-surface angle.
10/14/08
18
A- Minimum extensions:
The objective of modified design is to remove the fault as conservatively as possible. The design have neither specified cavity wall configuration nor specified pulpal depth and have enamel margins. N.B Axial walls may be composed partially or completely of enamel, because no extension for retention in dentin is required.
10/14/08
19
B- Beveled cavo – surface angle: The cavo-surface angle is beveled to a 45 degree angle and for a width of 0.5mm.
10/14/08
20
Advantages of beveling: 1- Improved peripheral seal and attachment, with improved adaptation and micromechanical retention as a result of: The increase in surface area of enamel available for bonding. Exposing the ends, rather than the sides, of enamel rods provides for more effective acid etching with creation of more numerous micro – and macro – pores. 10/14/08
21
Ends of enamel rods (A) are more effectively etched, producing deeper microundercuts than when only sides of enamel rods are etched 10/14/08
22
Advantages of beveling: 2- Improved esthetics: Bevel useful in gaining a gradual optical transition from composite to enamel. Contraindication for beveling of cavo–surface angle: Enamel walls that are located at high stress bearing areas, such as those of occlusal cavities and lingual cavities in upper anterior, to avoid marginal chipping of composite. (because of its brittleness) Cementum or thin enamel. (instead, gingival grooves, are incorporated and/or a glass ionomer cement liner is placed for retention and improved adaptation. 10/14/08
23
B- Bevelled conventional design
10/14/08
This design is indicated: When composite restoration is being used to replace an existing restoration exhibiting a conventional cavity preparation with enamel margin. When restoring a large carious lesion where the need for increased retention form is anticipated. 24
Manipulation:
10/14/08
Selection of composite, type and shade Field isolation Pulp protection Matricing and wedging. Pre-treatment of the substrate surface. Packing. Carving. Polymerization. Finishing and polishing. 25
Selection of composite:
The multipurpose system incorporating whole etchant, universal bonding agent and hybrid type composite are the preferable system. Composite are supplied in different shades and with a shade guide. The shade selection should be accomplished before the restorative procedure is initiated. Therefore, selection is made while the tooth is moist, before the cavity preparation, and before the rubber dam is placed. Desiccation of the tooth causes significant lightening of the shade, and the presence of a rubber dam can distort color perception
10/14/08
26
The selected shade can be confirmed with a small amount of composite (test shade) placed directly on or adjacent to the tooth and cured. This procedure should be performed on an unetched tooth surface to make removal easy after shade verification.
10/14/08
27
Selection of composite:
10/14/08
For class 4 restorations and others in which no tooth structure is remaining lingual to the composite, the test shade should be placed in the approximate thickness of the tooth structure to be replaced to assure adequate opacity or color density.
28
Field isolation
Composite is highly sensitive to moisture contamination which causes deterioration of its physical properties. In addition bonding to enamel and dentin is severely affected by moisture. Field isolation is best obtained using rubber dam which prevents moisture contamination and protects gingival tissues. In case of inability to establish a moisture free field, indirect rather than direct restorations are indicated
10/14/08
29
Field isolation
10/14/08
30
Pulpal protection
Protection against oral environmental irritants may be provided by: effective peripheral sealing with elimination of leakage sealing of tubular orifices by adhesives or cavity liners and bases (specially if they are antibacterial)
10/14/08
31
Pulpal protection
10/14/08
If used, calcium hydroxide should be limited to those areas of the preparation in which there is the potential for pulpal exposure. Placement of a CaoH liner over an extensive area of dentin decreases the surface area for adhesion, and dissolution of the liner during acid etching can interfere with a sound bond to enamel and dentin. 32
Pulpal protection
Although CaoH offers good protection, yet it dissolves under clinical restorations with gap formation (that can fill with tissue fluid and become secondarily infected under leaking restorations). If the preparation is conservative in size, no liner in addition to adhesive agent is required. In deeper preparations and those that approach or extend beyond the cemento-enamel junction, a glass-ionomer liner or base may be considered.
10/14/08
33
Pulpal protection
Glass-ionomer bounds to both tooth structure and composite. It releases fluoride into adjacent tooth structure. Use of a glass-ionomer liner has been demonstrated to improve marginal integrity and decrease marginal leakage. Less bulk of composite is required to fill the preparation, reducing the amount of polymerization shrinkage and improving marginal adaptation. Glass-ionomer liners also reduce the rise in pulpal temperature associated with application of the curing light during incremental insertion procedures.
10/14/08
34
Pulpal protection
However, with improvements in dentin adhesives, the use of glass-ionomer under composite restorations has been greatly reduced in recent years. Be aware: Enamel walls Should be kept Retentive grooves free of the liner Peripheral portion of gingival-dentin walls
10/14/08
35
Matricing and wedging:
Application of matrix may be essential especially with chemically-curable composites, in order to: Protect the adjacent tooth against accidental acid etching. Establish proper contour. Prevent marginal overhangs that may cause gingival irritation. Increase density and adaptation of the restoration by pressure application on composite during its polymerization that eliminate internal voids.
10/14/08
36
Matricing and wedging:
10/14/08
Prevent air-inhibited polymerization at the significant surface areas by protection coverage of the maturing resin.( When curing bonding layers or composites, the outermost layer will remain unpolymerized due to the inhibiting effect of oxygen in the adjacent air (air-inhibited layer). This 3-20 micron thick layer will cure as soon as oxygen is excluded. After adding all the increments, the outer most layer will remain sticky due to this air inhibition. This sticky layer is eliminated during finishing and polishing operations). Improve surface texture of composites and leave smooth as set surface that requires less finishing. 37
Matricing and wedging: Different types of matrices are available including: The Mylar matrix strip. Celluloid crown form. The compound-supported and wedged dead-soft metal matrix (suitable for compound cavities). The Howe circumferential plastic strip, ready-made (suitable for large compound preparations).
10/14/08
38
Matricing and wedging:
Usually a wedge (wood wedge for chemically curable composites, or a light-transmitting plastic wedge for VLC composite) is placed just gingival to this margin of proximal cavities to: Hold the strip in position. Prevent a gingival overhang of the material.
10/14/08
39
Matricing and wedging
10/14/08
40
Matricing and wedging:
Provide slight separation of the teeth (pre-wedging): Resin composite does not have the condensability that permits amalgam to deform a matrix band and maintain close adaptation to an adjacent tooth. Placement of an interproximal wedge at the start of the procedure is recommended to open the contact with the adjacent tooth and compensate for the thickness of the matrix band.
10/14/08
41
1
Advantages of resin composites 1- Superior esthetics; They have refractive index close to that of enamel and dentin combined. The compositional filler scatters the incident light producing excellent depth of translucency. They are available in all possible toothcolors. 10/14/08
2
Advantages of resin composites 2- Composites have low thermal conductivity and diffusivity. Therefore, they do not transmit thermal shocks to underlying dentin and pulp. 3- Satisfactory physical and mechanical properties; that are considered to be satisfactory for clinical applications. 4- Easy to repair. 5- Strengthening of the remaining tooth structure via bonding system. 6- Conservation of tooth structures. 10/14/08
3
Disadvantages of resin composites
10/14/08
1- Questionable adaptation a- High polymerization shrinkage. Composite resin exhibits a clinically polymerization shrinkage of about 1.5-3 vol%, that causes the maturing resin to pull off substrate enamel and dentin surfaces, with tensile stresses of 17-20 MPa. The shrinkage gaps invite leakage with ingress of oral environmental bacteria, fluids, and stains causing acute clinical problems of dentin hypersensitivity, adverse pulp reactions, and recurrent caries. It is for this purpose that adhesive systems are used. 4
Disadvantages of resin composites
B- Poor wettability It has low wettability, due to material high viscosity and surface tension. This inhibits the spontaneous flow of the material, and diffusibility into substrate enamel surface ( with low surface energy) and substrate dentin surface ( with low surface energy). Moreover, the material is hydrophobic, and therefore is easily displaced off substrate surface by compositional water. Therefore, effective adhesive systems must be used to promote resin wettability of substrate surface.
10/14/08
5
Be aware
Sufficient wetting of the adhesive will only occur if its surface tension is less than the surface-free energy of adherend ( substrate tooth substance ). High surface energy of adherend -----» able to attract the atoms of adhesive. Low surface tension and low viscosity of adhesive ----» able to properly wet the adherend.
10/14/08
6
Disadvantages of resin composites
C- High differential coefficient of thermal expansion Composites have higher coefficient of thermal expansion than that of the tooth. The closer the coefficient of thermal expansion of the material is to that of enamel, the less chance for creating opening at the junction of the material and the tooth when temperature changes occurs. Bonding a composite to etched tooth structure reduces the negative effects of a difference between coefficient of thermal expansion of the tooth structure and the material.
10/14/08
7
Disadvantages of resin composites 2- Low wear resistance; It leads to: Opening of interproximal contacts. Loss of anatomic form and of vertical dimension. Makes the restoration vulnerable to surface degradation by environmental fluids, food chewing and plaque bacterial metabolic activities.
10/14/08
8
Disadvantages of resin composites
3- Hydrolytic instability. Resin-based restorations are subjected in the mouth to time-dependent structural, interfacial, and surface deterioration by complex mechanisms of hydrolysis ( by environmental acids ), water sorption ( in oral environmental fluid ) and marginal percolation with progressive deterioration of marginal adaptation, wear and loss of strength.
10/14/08
9
Disadvantages of resin composites
10/14/08
4- Potentials for adverse pulp reactions. Adverse pulp reactions are more frequent under composite restorations. They were believed to be due to residual compositional constituents of composite resin. Recent researches have confirmed their bacterial etiology.
10
Disadvantages of resin composites
5- Technique sensitivity. It has potentials to exhibit significant variations in properties, handling characteristic, and clinical performance in response to deviations from manufacturer instructions relative to details of substrate surfaces pre-treatment and application of composite.
10/14/08
11
Disadvantages of resin composites
6- Lack of cariostatic potentials. Anticariogenicity through incorporation of fluorides has not been successful with composite because its extremely low solubility prevents sustained release of sufficient amount of fluoride ions.
10/14/08
12
Indications
10/14/08
1- Carious defects: Class I and II cavities that can be isolated properly and where centric contact (s) on tooth structure is (are) present. Class III, IV and V.
13
Indications
10/14/08
2- Non-carious lesions: Hypoplasia. Hypocalcification that is esthetically objectionable or is cavitated. Abrasion and erosive lesions. Class VI cavities ( faulty pit on selected occlusal cusps ). Abfraction lesion, ( cervical induced cavities owing to the flexure of teeth during function as a result of the presence of an occlusal interference ). 14
Indications Non-carious lesions
Enamel hypoplasia Abfraction 10/14/08
15
Indications
10/14/08
2- Non-carious lesions: Veneer for metal restorations. Repair of fractured areas. Core build-up. Cementation of orthodontic brackets. Luting purposes. Splinting of mobile teeth. Restoration of a weakened tooth that can be strengthened by a bonded restorations. 16
Contraindications
10/14/08
When the occlusal contacts will be on the composite material. Heavy occlusal stresses due to unfavorable occlusion. Deep subgingival areas that are difficult to prepare or restore. Poor oral hygiene. Wherever provision of dry field is not possible. Bruxing patients. 17
Designs of cavity preparation: A- Modified cavity design:
The introduction of adhesive practice i.e. bonding to enamel and dentin, has modified the classic cavity preparation in to what is known as the adhesive or conservative cavity design. These cavities are characterized by: A- Minimum extensions. B- Beveled cavo-surface angle.
10/14/08
18
A- Minimum extensions:
The objective of modified design is to remove the fault as conservatively as possible. The design have neither specified cavity wall configuration nor specified pulpal depth and have enamel margins. N.B Axial walls may be composed partially or completely of enamel, because no extension for retention in dentin is required.
10/14/08
19
B- Beveled cavo – surface angle: The cavo-surface angle is beveled to a 45 degree angle and for a width of 0.5mm.
10/14/08
20
Advantages of beveling: 1- Improved peripheral seal and attachment, with improved adaptation and micromechanical retention as a result of: The increase in surface area of enamel available for bonding. Exposing the ends, rather than the sides, of enamel rods provides for more effective acid etching with creation of more numerous micro – and macro – pores. 10/14/08
21
Ends of enamel rods (A) are more effectively etched, producing deeper microundercuts than when only sides of enamel rods are etched 10/14/08
22
Advantages of beveling: 2- Improved esthetics: Bevel useful in gaining a gradual optical transition from composite to enamel. Contraindication for beveling of cavo–surface angle: Enamel walls that are located at high stress bearing areas, such as those of occlusal cavities and lingual cavities in upper anterior, to avoid marginal chipping of composite. (because of its brittleness) Cementum or thin enamel. (instead, gingival grooves, are incorporated and/or a glass ionomer cement liner is placed for retention and improved adaptation. 10/14/08
23
B- Bevelled conventional design
10/14/08
This design is indicated: When composite restoration is being used to replace an existing restoration exhibiting a conventional cavity preparation with enamel margin. When restoring a large carious lesion where the need for increased retention form is anticipated. 24
Manipulation:
10/14/08
Selection of composite, type and shade Field isolation Pulp protection Matricing and wedging. Pre-treatment of the substrate surface. Packing. Carving. Polymerization. Finishing and polishing. 25
Selection of composite:
The multipurpose system incorporating whole etchant, universal bonding agent and hybrid type composite are the preferable system. Composite are supplied in different shades and with a shade guide. The shade selection should be accomplished before the restorative procedure is initiated. Therefore, selection is made while the tooth is moist, before the cavity preparation, and before the rubber dam is placed. Desiccation of the tooth causes significant lightening of the shade, and the presence of a rubber dam can distort color perception
10/14/08
26
The selected shade can be confirmed with a small amount of composite (test shade) placed directly on or adjacent to the tooth and cured. This procedure should be performed on an unetched tooth surface to make removal easy after shade verification.
10/14/08
27
Selection of composite:
10/14/08
For class 4 restorations and others in which no tooth structure is remaining lingual to the composite, the test shade should be placed in the approximate thickness of the tooth structure to be replaced to assure adequate opacity or color density.
28
Field isolation
Composite is highly sensitive to moisture contamination which causes deterioration of its physical properties. In addition bonding to enamel and dentin is severely affected by moisture. Field isolation is best obtained using rubber dam which prevents moisture contamination and protects gingival tissues. In case of inability to establish a moisture free field, indirect rather than direct restorations are indicated
10/14/08
29
Field isolation
10/14/08
30
Pulpal protection
Protection against oral environmental irritants may be provided by: effective peripheral sealing with elimination of leakage sealing of tubular orifices by adhesives or cavity liners and bases (specially if they are antibacterial)
10/14/08
31
Pulpal protection
10/14/08
If used, calcium hydroxide should be limited to those areas of the preparation in which there is the potential for pulpal exposure. Placement of a CaoH liner over an extensive area of dentin decreases the surface area for adhesion, and dissolution of the liner during acid etching can interfere with a sound bond to enamel and dentin. 32
Pulpal protection
Although CaoH offers good protection, yet it dissolves under clinical restorations with gap formation (that can fill with tissue fluid and become secondarily infected under leaking restorations). If the preparation is conservative in size, no liner in addition to adhesive agent is required. In deeper preparations and those that approach or extend beyond the cemento-enamel junction, a glass-ionomer liner or base may be considered.
10/14/08
33
Pulpal protection
Glass-ionomer bounds to both tooth structure and composite. It releases fluoride into adjacent tooth structure. Use of a glass-ionomer liner has been demonstrated to improve marginal integrity and decrease marginal leakage. Less bulk of composite is required to fill the preparation, reducing the amount of polymerization shrinkage and improving marginal adaptation. Glass-ionomer liners also reduce the rise in pulpal temperature associated with application of the curing light during incremental insertion procedures.
10/14/08
34
Pulpal protection
However, with improvements in dentin adhesives, the use of glass-ionomer under composite restorations has been greatly reduced in recent years. Be aware: Enamel walls Should be kept Retentive grooves free of the liner Peripheral portion of gingival-dentin walls
10/14/08
35
Matricing and wedging:
Application of matrix may be essential especially with chemically-curable composites, in order to: Protect the adjacent tooth against accidental acid etching. Establish proper contour. Prevent marginal overhangs that may cause gingival irritation. Increase density and adaptation of the restoration by pressure application on composite during its polymerization that eliminate internal voids.
10/14/08
36
Matricing and wedging:
10/14/08
Prevent air-inhibited polymerization at the significant surface areas by protection coverage of the maturing resin.( When curing bonding layers or composites, the outermost layer will remain unpolymerized due to the inhibiting effect of oxygen in the adjacent air (air-inhibited layer). This 3-20 micron thick layer will cure as soon as oxygen is excluded. After adding all the increments, the outer most layer will remain sticky due to this air inhibition. This sticky layer is eliminated during finishing and polishing operations). Improve surface texture of composites and leave smooth as set surface that requires less finishing. 37
Matricing and wedging: Different types of matrices are available including: The Mylar matrix strip. Celluloid crown form. The compound-supported and wedged dead-soft metal matrix (suitable for compound cavities). The Howe circumferential plastic strip, ready-made (suitable for large compound preparations).
10/14/08
38
Matricing and wedging:
Usually a wedge (wood wedge for chemically curable composites, or a light-transmitting plastic wedge for VLC composite) is placed just gingival to this margin of proximal cavities to: Hold the strip in position. Prevent a gingival overhang of the material.
10/14/08
39
Matricing and wedging
10/14/08
40
Matricing and wedging:
Provide slight separation of the teeth (pre-wedging): Resin composite does not have the condensability that permits amalgam to deform a matrix band and maintain close adaptation to an adjacent tooth. Placement of an interproximal wedge at the start of the procedure is recommended to open the contact with the adjacent tooth and compensate for the thickness of the matrix band.
10/14/08
41
