Oral and Maxillofacial Imaging and Diagnosis
What the exam tests
This domain tests image selection, radiation protection, interpretation and the limits of each modality. The exam expects justification of every exposure and recognition of artifacts and anatomical landmarks.
Core rules and concepts
- Selection criteria: choose the modality that answers the clinical question with the lowest reasonable dose. Intraoral radiographs suit caries and periapical assessment; panoramic images survey the jaws and third molars; CBCT provides three-dimensional bone and canal anatomy; CT and MRI answer soft-tissue or extensive disease questions.
- ALARA and justification: every exposure needs a clinical indication; repeat only when the result will change management. Use rectangular collimation, thyroid shielding where appropriate and optimized exposure settings.
- CBCT: know the limited field of view and effective dose; beam-hardening and movement artifacts degrade images. Do not use CBCT as a routine substitute for intraoral radiographs.
- Panoramic interpretation: recognize ghost images, palate superimposition and positioning errors; a ghost image appears on the opposite side and higher.
- Diagnosis: combine history, clinical examination, imaging and, when needed, biopsy or fine-needle aspiration. Imaging alone rarely gives a definitive histological diagnosis.
Worked example
A panoramic radiograph shows a radiolucency at the apex of 46, but the tooth is asymptomatic and the image is blurred. Reasoning: first obtain a periapical radiograph with good technique; if the lesion is confirmed and its relation to the inferior alveolar canal or cortical plates matters, consider a small-field CBCT. Do not repeat the panoramic image.
Traps
Ordering CBCT for every endodontic case; misreading ghost images as pathology; ignoring radiation dose; repeating radiographs without a management change; accepting a blurred image as diagnostic.