Periapical radiography

Main indications Detection of periapical infection Assessment of the periodontal status After trauma to the teeth and associated alveolar bone Assessment of the presence and position of unerupted teeth

During endodontics Preoperative assessment and postoperative appraisal of apical surgery Detailed evaluation of bone lesions Implant evaluation

Ideal positioning requirements The tooth under investigation and the film packet should be in contact or ,if not feasible, as close as possible The tooth and the film packet should be parallel to one another

The film packet should be positioned with its long axis vertically for incisors and canines, and horizontally for premolars and molars with sufficient film beyond the apices to record the apical tissues The positioning should be reproducible

The X-ray tubehead should be positioned so that the beam meets the tooth and the film at right angles in both the vertical and the horizontal planes

Positioning of the instrument

Theoretical basis of the bisected angle technique

Advantages of the paralleling technique Geometrically accurate images are produced with little magnification, foreshortening or elongation The shadow of the zygomatic buttress appears above the apices of the molar teeth

The horizontal and vertical angulations of the X-ray tubehead are automatically determined by the positioning device There is no cone cutting The radiographs are reproducible The technique is useful for some patients with disabilities

Disadvantages of the paralleling technique Positioning of the film packet for the posterior teeth can cause gagging The anatomy of the mouth sometimes makes the technique imposible, e.g a shallow, flat palate The apices of the teeth can sometimes appear very near the edge of the film

The technique cannot be performed satisfactory using a short focal spot to skin distance because of the resultant magnification The holders need to be autoclavable Positioning the holders in the lower third molar region can be very difficult

Advantages of the bisected angle technique Positioning of the film packet is relatively simple and comfortable for the patient If the angulations are assessed correctly the image should be diagnosticable

Disadvantages Incorrect vertical angulation results in foreshortening or elongation of the image The shadow of the zygomatic buttress overlies the roots of the upper molars Incorrect horizontal angulation results in overlapping of the crowns or cone cutting

The periodontal bone levels are poorly shown It is not possible to obtain reproducible views The buccal roots of the maxillary premolars and molars are foreshortened