Localization Techniques

Bisecting angle

May have correct length but there is distortion at apical region

Bisecting angle

Film is manually held in patient’s mouth

Bisecting angle

Tendency of the film to be deformed

Bisecting angle

Problem is superimposition of other structures

Paralleling

Produce better diagnostic images; no elongation

Paralleling

Use of paralleling device

Paralleling

No film deformity but possible problem is the space inside the patient’s mouth

Paralleling

Less exposure to critical organs such as thyroid gland and eyes

Bitewing examinations

Presence of interproximal caries

Bitewing examinations

Pulp size and pulp changes

Bitewing examinations

Overhanging restorations

Bitewing examinations

Recurrent caries

Bitewing examinations

Calcular deposits

Bitewing examinations

Height of alveolar bone

Localization technique

Used to locate the object of interest (if it is at the buccal or lingual only or labial or palatal)

Definitive evaluation method

Based on shadow casting principles

An object positioned farther away from the image receptor

will be magnified and less clear

Intraoral image receptor placement

positions the receptor close to the lingual surface of the teeth

Objects on the lingual

are more likely to appear distinctly defined on the resultant radiograph

Definitive method of localization

is not consistently reliable

Right-angle technique (occlusal projection)

Primarily identifies buccolingual location

Right-angle technique (occlusal projection)

may also confirm mesiodistal location seen on periapical

Right-angle technique (occlusal projection)

Utilizes a cross-sectional occlusal radiograph

Tube-shift technique (Frank’s shift, Clark’s shift)

Also known as buccal-object rule

Tube-shift technique (Frank’s shift, Clark’s shift)

Utilizes two films with different horizontal or vertical angulations

Structures nearest to the film

are clearer

Films

are always positioned on the lingual (nearest to the tongue)

Right angle technique

2 radiographs are used

Right angle technique

2nd radiograph

SLOB rule (Clark’s shift)

Same Lingual Opposite Buccal

SLOB rule

used to identify the buccal or lingual location of objects in relation to a reference object

If the image of an object moves mesially when the tubehead is moved mesially

the object is located on the lingual

If the image of the object moves distally when the tubehead moves mesially

the object is located on the buccal

Horizontal movement

Tubehead is moved either anteriorly or posteriorly

Tubehead is moved anteriorly

tubehead is moved towards mesial

Tubehead is moved posteriorly

tubehead is moved towards distal

Frank’s shift

Take 2 radiographs at different vertical angulation while maintaining the same horizontal angulation