Bisecting technique

Question 1

basic concepts of bisecting technique

Answer 1

• another method than can be used to expose periapical films
• NO RINN KIT
• only use film holder
• must limit distortion of film
• use bisecting angles b/w film and tooth to direct the central ray

Question 2

why do we use the bisecting technique?

Answer 2

• must use technique when film can not be held parallel to the tooth
• if no RINN kit available
• if film extremely uncomfortable and/or causing gagging with RINN kit

Question 3

terminology for bisecting technique

Answer 3

• angle
• bisect
• triangle
• triangle, equilateral
• triangle, right
• triangles, congruent
• hypotenuse
• isometry
• long axis of the tooth

Question 4

what is the rule of isometry?

Answer 4

• two triangles are equal if they have 2 equal angles and share a common side

Question 5

how is the rule of isometry applied to the bisecting technique?

Answer 5

• the central ray is not perpendicular with the film, but the angle between the film and the tooth is bisected (imaginary)
• two resultant triangles are right angles and congruent

Question 6

why is the rule of isometry so important in the bisecting technique?

Answer 6

• the radiographic image will turn out accurate and diagnostic
• when done properly, a tooth and its radiographic image will be equal in length when 2 equal triangles are formed that share a common side (imaginary bisector)

Question 7

what is a film holder?

Answer 7

• a device used to position an intraoral film in the mouth
• recommended because they eliminate the need for the patient to stabilize the film
• film holder reduce the patient exposure to radiation

Question 8

what is the finger-holding technique?

Answer 8

• patient’s finger or thumb is used to stabilize the periapical film
  NOT RECOMMENDED
• film holders reduce the patient’s exposure to radiation

Question 9

common film holders:

Answer 9

A - Rinn BAI
B - Stabe bite blocks
C - Eezee Grip (Snap-A-Ray)
D - Foam Tabs

Question 10

what size films are used for the bisecting technique and what part of the mouth are they used for?

Answer 10

size 1 and 2 film

• anterior: size 1, vertical placement
• posterior: size 2, horizontal placement

Question 11

what is angulation?

Answer 11

• describes the alignment of the central ray of the x-ray beam in the horizontal and vertical planes
• angulation can be varied by moving the PID in either a horizontal or a vertical direction

Question 12

what is horizontal angulation? what is correct and incorrect horizontal angulation?

Answer 12

• the positioning of the tubehead and direction of the 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 teeth
• incorrect horizontal angulation: overlapped contact areas (cannot be used to examine the interproximal areas of the teeth)

Question 13

what is vertical angulation?

Answer 13

• the positioning of the PID in a vertical or up and down plane
• in paralleling: directed at film at 90 degrees
• in bisecting: directed at imaginary bisecting angle (not the film). the central ray is directed perpendicular to the imaginary bisector (90 degrees). is measured in degrees and is registered on the outside of the tubehead
• correct vertical angulation results in image that is the same length as the tooth

Question 14

what is positive vertical angulation?

Answer 14

when the tubehead is too high up

Question 15

what is negative angulation?

Answer 15

when the tubehead is too low

Question 16

what will result from incorrect vertical angulation in the positive. angulation?

Answer 16

foreshortened images

• teeth appear shortened
• results from excessive vertical angulation

Question 17

what will result from incorrect vertical angulation in the negative angulation?

Answer 17

elongated images

• teeth appear too long
• results from insufficient vertical angulation

Question 18

rules for bisecting technique: film placement and film position

Answer 18

• film placement: same as parallel
• film position: along the lingual of the tooth - as close as possible. Dot - 1/8 inch beyond occlusal plane
• vertical angulation: central beam perpendicular to bisecting angle
• horizontal angulation: open contacts - central ray of the x-ray beam must be directed through the contact areas between the teeth

Question 19

step-by-step procedures

Answer 19

• patient preparation
• equipment preparation
• exposure sequence for film placements
• film placement

Question 20

patient preparation

Answer 20

• infection control procedures
• preparation of treatment area and supplies
• patient is seated
• patient is prepared

Question 21

patient preparation for bisecting technique:

Answer 21

• explain the radiographic procedure
• position the patient in the cair
• adjust the headrest
• place and secure the lead apron with thyroid collar
• remove all objects from the patient’s mouth

Question 22

equipment preparation

Answer 22

• set exposure factors

- open the sterilized package containing the film holder if film holders are used

Question 23

exposure sequence for film placements in anterior teeth

Answer 23

anterior exposure sequence:

• begin with mx right canine tooth, expose all mx anterior teeth, end w mx left canine
• move to mn arch, begin w mn left canine, expose all the mn anterior teeth, end w mn right canine

Question 24

exposure sequence for film placements in posterior teeth

Answer 24

posterior exposure sequence

• begin w mx right quadrant
• move to mn right quadrant
• move to mx left quadrant
• finish w mn left quadrant
• • in each quadrant, expose the premolar film first then the molar film

Question 25

what is film placement?

Answer 25

the specific area where the film must be positioned before exposure - dictated by the teeth and surrounding structures that must be included on the resultant radiograph

Question 26

advantages of the bisecting technique:

Answer 26

- can be used without a film holder | - reduce gagging and discomfort

Question 27

disadvantages of the bisecting technique:

Answer 27

- image distortion - angulation problems - unnecessary exposure (if pt finger is used, also increase retakes)