Radiology- Bisecting Technique Chapter 20

Bisecting technique

another method that can be used to expose periapical images, faster technique

Bisector

a ray that divides an angle into two congruent angles

Angle

A figure formed by two rays with a common endpoint

Triangle

a three-sided polygon

equilateral triangle

3 congruent sides

right angle

an angle that measures 90 degrees

Long axis of the tooth

an imaginary line that divides the tooth longitudinally into two equal halves

Central Ray

The central portion of the primary beam of radiation.

rule of isometry

two triangles are equal if they have two equal angles and share a common side

-in dental imaging this geometric principle is applied to bisecting material to form two imaginary equal triangles

Bisecting technique steps

1. the receptor must be placed along the lingual surface of the tooth

2. the plane of the receptor and the long axis of tooth form an angle at point where the film contacts tooth

3. Imaginary bisector bisects the angle formed by the receptor and the long axis of tooth

4.the cental ray is directed perpendicular to the imaginary bisector

5. the two imaginary triangles that result are right triangles and congruent

Receptor holding device

used to position the receptor in the mouth and maintain it in position during exposure

-Stabe bite block

-Rinn Snap-A-Ray Holder

Receptors used for bisecting technique

Size 2 receptor used traditionally

-Anterior - long portion in a vertical direction

-Posterior - long portion is a horizontal direction

Horizontal angulation

the positioning of the tubehead and direction of the central ray in a horizontal or side-to-side plane

Correct horizontal angulation

The central ray is directed perpendicular to the curvature of the arch and through the contact areas of the teeth

Incorrect horizontal angulation

Overlapped contact areas

Vertical angulation

Refers to the positioning of the PID in a vertical, or up-and-down, plane

Correct vertical angulation

Results in a radiographic image that is the same length as the tooth

Incorrect vertical angulation

Results in a radiographic image that is not the same length as the tooth

Foreshortened image

results from excessive vertical angulation

Elongated images

results from insufficient vertical angulation

bitewings are supposed to be

10 degree angulation

Steps of bisecting technique simplified

1. receptor placement

2. receptor position

3. vertical angulation

4. horizontal angulation

5. receptor exposure

Patient preparation

Infection control procedures

Preparation of treatment area and supplies

Patient is seated

Patient is prepared

Exposure Sequence for Receptor Placements

anterior exposure first, then posterior due to the anterior being easier for the patient to tolerate and get used to