This document discusses techniques for localizing objects in intraoral radiography. It describes the right-angle technique using two films projected at right angles to determine an object's position. It also explains the tube shift technique, also known as Clark's rule, where comparing how an object's position changes relative to a reference object when the tube is shifted can determine if the object is lingual or buccal. The document provides examples of applying these techniques to locate impacted teeth, foreign objects, and abnormalities.

1. Object Localization in
inraoral radiography

2. Aim:
• To obtain three-dimensional information
concerning patients

3. Methods:
• 1-examine two films projected at right
angles to each other.
• In clinical practice the position of an
object on each radiograph is noted
relative to the anatomic landmarks.
This allows the observer to determine
the position of the object or area of
interest

4. An example:

5. Note:
• The right-angle (or cross-section)
technique is best for the mandible.
• On a maxillary occlusal projection the
superimposition of features in the
anterior part of the skull may frequently
obscure the area of interest.

6. 2-tube shift technique.
• Other names for this procedure are the
buccal object rule and Clark ’ s rule .
• The rationale for this procedure derives
from the manner in which the relative
positions of radiographic images of two
separate objects change when the
projection angle at which the images were
made is changed.

7. • If the tube is shifted mesially and the
object in question also moves mesially
with respect to the reference object, the
object lies lingual to the reference object.
• Alternatively, if the tube is shifted
mesially and the object in question
appears to move distally, it lies on the
buccal aspect of the reference object

8. • These relationships can be easily
remembered by the acronym SLOB :
S ame L ingual, O pposite B uccal.

9. An example of a lingually object:

10. An example of a bucally object:

11. • Examination of a conventional set
of full-mouth films with this rule in
mind demonstrates that the
incisive foramen is indeed located
lingual (palatal) to the roots of the
central incisors and that the
mental foramen lies buccal to the
roots of the premolars.

12. This technique assists in:
• determining the position of impacted teeth,
• the presence of foreign objects,
• and other abnormal conditions.

13. Example:
• The dentist may have two
radiographs of a region of the
dentition that were made at
different angles, but no record
exists of the orientation of the x-
ray machine.

14. • Comparison of the anatomy
displayed on the images helps
distinguish changes in horizontal
or vertical angulation.
• The relative positions of osseous
landmarks with respect to the teeth
help identify changes in horizontal
or vertical angulation.

15. In these images,inferior border of
the zygomatic process of the maxilla
castsover the molars:

16. • This structure lies buccal to the teeth
and appears to move mesially as the x-
ray beam is oriented more from the
distal.
• Similarly, as the angulation of the
beam is increased vertically, the
zygomatic process is projected
occlusally over the teeth.

17. LOCALIZATION OF THE
INFERIOR ALVEOLAR CANAL
• Traditional panoramic imaging may be
adequate when the third molar is clear of
the canal, but in the case of radiographic
superimposition it is advisable to use a
3D imaging approach.

18. • This can be achieved at comparatively low
radiation dose with CBCT combined either
with the proprietary software
accompanying the imaging device or with
a third-party diagnostic software

19. Panoramic view of lower third molar

20. CBCT of previos tooth

21. A case of radiopaque sialolith:

22. Periapical radiographies:

23. Occlusal view:

24. Computed tomography view

25. • Thanks for your attention