Oblique lateral radiography
Oblique lateral radiographs are extraoral views of the jaws that can be taken using a dental X-ray set (see Fig. 10.1). Before the development of panoramic equipment they were the routine extraoral radiographs used both in hospitals and in general practice. In recent years, their popularity has waned, but the limitations of panoramic radiographs (see Ch. 12) have ensured that oblique lateral radiographs still have an important role.
Lateral radiographs of the head and jaws are divided into:
The differentiating adjectives true and oblique are used to indicate the relationship of the film, patient and X-ray beam, as shown in Fig. 10.2.
True lateral positioning
The image receptor and the sagittal plane of the patient’s head are parallel and the X-ray beam is perpendicular to both of them. This is the positioning for the true lateral skull radiograph taken in a cephalostat unit described in Chapter 11.
Oblique lateral positioning
The image receptor and the sagittal plane of the patient’s head are not parallel. The X-ray beam is aimed perpendicular to the image receptor but is oblique to the sagittal plane of the patient. As a result, a variety of different oblique lateral projections is possible with different head and X-ray beam positions.
The main clinical indications for oblique lateral radiographs include:
• Assessment of the presence and/or position of unerupted teeth
• Detection of fractures of the mandible
• Evaluation of lesions or conditions affecting the jaws including cysts, tumours, giant cell lesions, and osteodystrophies
• As an alternative when intraoral views are unobtainable because of severe gagging or if the patient is unable to open the mouth or is unconscious (see Ch. 6, Fig. 6.1)
• As specific views of the salivary glands or temporomandibular joints.
This includes (see Fig. 10.3):
Fig. 10.3 Equipment used for oblique lateral radiography. (i) An 11 × 18 cm cassette A and lead shield B. (ii) An example of an angle board showing the cassette A, lead shield B and the plastic earpieces P for patient positioning.
• An extraoral cassette containing film and intensifying screens or a digital phosphor plate (usually 13 × 18 cm)
• A lead shield to cover half the cassette when taking bimolar views.
Specially constructed angle boards, as shown in Fig. 10.3, can be used to facilitate positioning, but are not considered necessary by the authors.