Bisecting And Parelling Technique.ppt

“Image receptor is placed inside the mouth and x-rays are directed from outside the mouth”

Extra-oral Radiography

Intra-oral Radiography

“Image receptor is placed outside the mouth and x-rays, too, are directed from outside the mouth” Dr rupam sinha

Intra-oral Radiography Periapical

Bitewing

Occlusal Dr rupamsinha

Description of a Radiographic Technique # # # # #

Patient Position Placement of Image Receptor Direction of the Central Ray Point of Entry / Centering Point Exposure Parameters: Tube voltage (kVp), Tube current (mA), Exposure time (S), Target to image receptor distance (TID / TFD), Size and type of image receptor

General Considerations in Intra-oral Radiography  Follow the Infection Control protocol.  Follow the methods of Radiation Protection. Provide a leaded apron to every patient irrespective of age and sex.  Prior and careful explanation of the procedure will make the patient relaxed, comfortable, confident of your ability, and therefore, cooperative.  Eyeglasses, nose ornaments and removable dentures should be removed prior to exposure.  Immobilize the patient to avoid repeat exposure.

General Considerations in Intra-oral Radiography  Carry out the easier and more comfortable techniques first.  Film should remain flat as far as possible. Gentle bending (not ‘folding’) of the corners may avoid tissue injury and gagging.  Process under standardized conditions to achieve consistent good quality.  Interpret under ideal viewing conditions to obtain maximum useful information. Remember! Radiographs are to be made only when benefits from them far outweigh the damages from radiation exposure.

Intra-oral Periapical Projection “To record images of teeth; periapical and periodontal alveolar bone” Two Techniques ‘Paralleling Cone’ Technique (Long cone technique)

‘Bisecting - the angle’ Technique (Short cone technique)

Paralleling Cone Technique of Intra-oral Periapical Radiography described by Edmund in 1896 1. Patient•First Position: Patient can C.beKells either sitting McCormack 1937 upright or •Revived reclinedbyinDonald the dental chair inprovided that Fitzgerald in 1947 the head is•Perfected not tiltedbytoGordon the side.

2. Placement of Image Receptor: Image receptor is placed parallel to the long axis of the tooth to be radiographed. Special devices are used to achieve and maintain the correct receptor position.

OMR, CODS, DVG

Requirements for Receptor Holders: ~ Should be rigid ~ Should be autoclavable ~ Should be small and lightweight ~ Should maintain parallelism between tooth and receptor ~ Should align the central ray perpendicular to the receptor Types of Receptor Holders:

~ Artery forceps with a bite block ~ ‘Snap-a ray’ instrument ~ ‘XCP’ device

Snap-A-Ray Instrument

XCP (extension cone paralleling) Instruments

Artery forceps or

needle holder

3. Direction of the Central Ray: The central ray should be perpendicular to both- the image receptor and the long axis of the tooth in both -vertical and horizontal planes.

Horizontal

Vertical

4. Point of Entry / Centering Point: Maxillary teeth > Along the ala-tragus line Mandibular teeth > Along a line 3 cms above the inferior border of mandible 5. Exposure Parameters: kVp = 80 / 65 mA = 10 Exposure time (in seconds)

80 kVp

65 kVp

maxillary anterior teeth maxillary posterior teeth

1/4 1/3

1/2 3/4

mandibular anterior teeth mandibular posterior teeth

1/6 1/4

2/5 1/2

TID = 40 cms Type & size of image receptor : ‘E’ speed nonscreen film; No. 1 for anterior teeth, No. 2 for posterior teeth

Advantages: related to image quality  Better image quality i.e. sharper image with least image size and shape distortion.  Detection of early caries at the D-E junction and at the proximal surfaces possible due to perfect superimposition of buccal cusps over the lingual cusps.  Detection of early periodontal disease possible due to perfect superimposition of buccal alveolar crest over the lingual alveolar crest.  Avoids superimposition of zygomatic process of maxilla over the periapical region of maxillary molars.

OMR, CODS, DVG

Advantages: related to patient protection Less radiation due to: ~ higher kVp

~ more TID ~ less vertical angulation ~ patient in reclining position.

Advantages: general ~ Technique can be executed in any patient position.

Limitations:  Difficult to master.  Difficult to practice in endodontics.  Needs special receptor holders.  More number of exposures needed for a FMRS.

OMR, CODS, DVG

Bisecting - the Angle Technique of Intra-oral Periapical Radiography 1. Patient Position: Patient is made to sit upright in the dental chair with sagittal plane perpendicular to the floor. For maxillary teeth, Price the in ala-tragus line is •First described by Weston 1904 •Independently described by Cieszynskiteeth, in 1907lower kept parallel to floor. For mandibular •Also called asistechnique basedtoonfloor. Principle of border of mandible kept parallel Triangulation 2. PlacementIsometric of Image Receptor: Image receptor is placed close to the teeth making an angle at the occlusal level with the long axis of the tooth to be radiographed. The receptor extends beyond the occlusal plane by 5 mm. Receptor position is maintained either with patient’s finger or with a holder.

Image size <=Object Image size> Objectsize size

3. Direction of the Central Ray: Central ray is directed perpendicular to the teeth in the horizontal plane.

Angulation in the vertical plane: Teeth Angulation Maxillary Mandibular Incisors Canines Premolars Molars

+ 40 + 45 + 30 + 25

-15 - 20 - 10 - 05

Hi!

4. Point of Entry / Centering Point: ¶ Maxillary ‘line of concentration’ (MYLOC) is the imaginary ala-tragus line. ¶ Mandibular ‘line of concentration’ (MRLOC) is an imaginary line 1 cm above the inferior border of mandible.

Centering Points for Maxillary Teeth 11 18

12

16, 17 14, 15

13

Centering Points for Mandibular Teeth

44, 45 41

48

43 42

46, 47

Bye!

5. Exposure Parameters: kVp = 65, mA = 10, Exposure time in Seconds: Mandibular anteriors

:

0.1

:

0.2

Mandibular posteriors and Maxillary anteriors Maxillary posteriors TID = 20 cms

:

0.3

Type & size of image receptor: ‘E’ speed

non-screen film; No. 1 for anteriors, No. 2 for posteriors

Bisecting-the Angle Technique of Intra-oral Periapical Radiography

Limitations: related to image quality  Poorer image quality with size and shape distortion.  Detection of early caries and of early periodontal disease not possible.  Zygomatic process of maxilla superimposes over the periapical region of maxillary molars. Limitations: related to patient protection More patient exposure due to lower kVp shorter TID more vertical angulation patient in upright position.

Bisecting-the Angle Technique of Intra-oral Periapical Radiography

Limitations: general  technique must be executed with patient in upright position. Advantages: Easy to master. Easy to practice in endodontics. Does not need special receptor holders. Less number of exposures needed for a FMRS.

T H E R E F O R E

Paralleling cone technique is the technique Bisecting-the angle technique is to be used of choice for periapical radiography. only when the paralleling cone technique is not feasible.

Full Mouth Radiographic Survey (‘FMRS’) A ‘FMRS’ is a radiographic examination of the entire dentition and its supporting structures or of the edentulous alveolar processes. ‘FMRS’ consists of EITHER 10 to 16 periapical radiographs with 2 to 5 bitewing radiographs, OR 6 topographic occlusal radiographs with 2 bitewing radiographs, OR A panoramic radiograph with 2 to 5 bitewings radiographs.