Object Localization in inraoral radiography

Aim:

• To obtain three-dimensional information concerning patients

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

An example:

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.

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.

• 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

• These relationships can be easily remembered by the acronym SLOB :

S ame L ingual, O pposite B uccal.

An example of a lingually object:

An example of a bucally object:

• 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.

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

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.

• 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.

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

• 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.

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.

• 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

Panoramic view of lower third molar

CBCT of previos tooth

A case of radiopaque sialolith:

Periapical radiographies:

Occlusal view:

Computed tomography view

• Thanks for your attention