Department Of Oral Medicine & Radiology
2010-2011
OBJECT LOCALIZATION TECHNIQUES
Submitted
by
Shabhana . B
IV th BDS, Part 1.
Contents
1. Introduction
2. Indications
3. Localization Technique
4. Tube Shift Technique
5. Right Angle Technique
6. Stereoscopy
7. Radiographic Technique for Localization of Impacted Teeth & Foreign Bodies
8. Conclusion
9. Bibliography
Introduction
· These are methods to locate the position of a tooth or an object in the jaws.
· The dental radiograph is a two dimensional picture of a three dimensional object, it depicts the object in the superior – inferior and antero posterior relationship.
· It fails to depict buccolingual relation or depth of the object.
· Localization is used to overcome this lacune.
Indications
· Foreign bodies
· Impacted Teeth
· Unerupted Teeth
· Retained Roots
· Salivary Stones
· Jaw Fractures
· Broken needles and instruments
· Root positions
· Filling Materials
Localization Techniques
1. Tube shift technique [Buccal object rule or clarks rule]
2. Right angle technique
3. Stereoscopy
Tube shift technique
· Buccal object rule or clarks rule
· The basic principle is that relative position of the radiographic images of two separate objects changes when the projection angle at which the project was made is changed.
· Different horizontal angle used when trying to locate vertically aligned images. Example: Root Canals.
· Different vertical angle is used trying to locate a horizontally aligned images. Example: Mandibular Canal.
Method
· Two radiographs of the object taken.
· First radiograph with proper technique and angulation as prescribed.
· Second radiograph is with changing the direction of the central ray either with a different horizontal or vertical angulation and keeping all other parameter equivalent to the first radiograph.
Interpretation
· If the dental structure seen in the second radiograph appears to have moved in same direction as the shift of PID, the object in question is said to be positioned lingually.
· If the object appears to have moved in a direction opposite to the shift of PID, then object in question is said to be positioned buccally.
· SLOB rule – SAME SIDE LINGUAL OPPOSITE SIDE BUCCAL.
Right Angle Technique
· Here two projections are taken at right angles to each other which helps to localize an object in the maxilla or mandible.
Method
· A periapical radiograph is taken to show the position of the object superior-inferiorly and anterio posteriorly.
· Next occlusal radiograph is taken, which will show the object’s buccolingual and anterio posterior relationship.
· Two radiographs when studied together, helps to localize the objects in all three dimension.
Stereoscopy
· It is used to determine the location of small intracranial calcification and multiple foreign bodies in dense or thick section.
· Also used in cases in which the interpretation of images produced at right angle might be difficult.
· Evaluate the relationship of margins of bony fractures.
· Stereoscopic imaging requires the exposure of two films, one for each eye and thus deliver twice amount of radiation to patient.
· Between exposure, patient is maintained in position, film is changed, the tube is shifted from right eye to left eye position.
· After processing, the film are viewed with a stereoscope that uses either mirrors or prisms to coordinate the accommodation and convergence of the viewers eye, so that brain can fuse the two images.
· This technique is popular for the evaluation of bony pockets in patient with periodontal diseases.
· For morphology of temperomandibular joint area.
· Determination of root configuration of the teeth that require endodontic therapy.
· Assessment of the relationship of the mandibular canal to the root of the unerupted mandibular third molars.
· Assessment of bone shape when the placement of dental implant is considered.
Radiographic Techniques For Localization Of Impacted Teeth & Foreign Bodies
Maxillary Area
1. Incisor Zone
· Stereoscopic
· Lateral profile
· Occlusal
2. Cuspid Zone
· Stereoscopic
· Lateral profile
· Occlusal
3. Bicuspid & Molar Zone
· Periapical
· Occlusal
Mandibular Area
1. Incisor Zone
· Periapical
· Lateral profile
· Occlusal
2. Posterior Zone
· Occlusal
· Periapical
3. Third Molar Zone
· Periapical
· Lateral Oblique
· Oblique Occlusal
Conclusion
· In clinical practice, the dentist must often derive from a radiograph three dimensional information concerning patients.
· This two methods, right angle technique and tooth shift technique are frequently used to obtain such three dimensional information.
· The dentist may wish to use radiograph to determine the location of a foreign object or an impacted tooth within jaw.
Bibliography
· Dental & Maxillo Facial Radiology (2nd Edition)
Chapter Number, Page Number.
By Freny R Karjodkar
· Oral Radiology Principles & Intrepretation (6th Edition)
Chapter Number, Page Number
By Stuart C White, Michael J Pharoah
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