Kamis, 09 Agustus 2012

Intraoral Radiographic Techniques (Bitewing Radiography)-Chapter 4

Bitewing Radiography
Bitewing radiographs are of particular value in detecting interproximal caries in the early stages of development, before it is clinically apparent.  For this reason it is critical that horizontal angulation be accurately projected following the direction of the interproximal contacts and no overlapping contacts be present on the film.  Bitewing films are also useful in evaluation of the alveolar crests for detection of early periodontal disease.

Basic Principles
Bitewing radiographs are parallel films because the film is positioned parallel to the long axis of the teeth and the beam is perpendicular to the film as in Figure 59.  A bitewing tab is utilized to stabilize the film as the patient bites together (Figure 60).

Figure 59

Figure 60
Beam Angulation and Film Holding Devices

Bitewing radiographs are usually exposed with an indicated vertical angulation of +10 degrees (tube head points down for positive (+) angulation). This, angulation provides an acceptable compromise for the differences between the long axis inclinations of the maxillary and mandibular teeth.  Horizontal angulation is aligned with the direction of the contact, and the central ray is directed between the contact of the teeth to be radiographed.  Horizontal angulation is achieved when the central ray of the x-ray beam is directed specifically between the contacts of the teeth to be radiographed.
The interproximal examination may be done using special #3 bitewing film but is preferably achieved by using #2 films fitted with a tab.  There are also film holding devices available that support the film as well as provide an external reference for positioning the tube head.  The patient stabilizes the film by gently biting together on the manufactured tab or on the instrument.
Tube head position is illustrated in Figure 61, and a sample set of bitewing radiographs is illustrated in Figure 62.
Before any radiographs are exposed, the patient must be protected with a lead apron and thyroid collar. The apron must be properly placed to avoid interference with the radiographic exposure.
Figure 61
Figure 62
  1. What is the main purpose for taking bitewing radiographs?
  2. Why are bitewings exposed with a vertical angulation of +10 degrees?

  1. To detect interproximal caries.
  2. To compromise for the differences in the long axis angulations of the maxillary and mandibular teeth.

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