Oral Medicine, Oral Pathology and Oral Radiology
This domain tests whether you can move from a described lesion to a differential diagnosis, a biopsy decision and a radiographic interpretation. Persistent ulcers, red and white patches, vesiculobullous disease and pericoronal radiolucencies are the recurring themes.
Ulcers and mucosal lesions
- Any ulcer persisting beyond two weeks without an identifiable cause requires biopsy to exclude squamous cell carcinoma; induration, fixation and rolled margins raise suspicion.
- Leukoplakia is a diagnosis of exclusion; erythroplakia carries a higher risk of malignant transformation and must be biopsied.
- Oral lichen planus typically shows bilateral reticular striae; erosive forms need biopsy and topical corticosteroid therapy.
- Pseudomembranous candidiasis wipes off leaving erythema; erythematous and angular forms are often denture or steroid related.
Vesiculobullous and salivary disease
- Pemphigus vulgaris shows suprabasal acantholysis with intercellular IgG on direct immunofluorescence; mucous membrane pemphigoid shows subepithelial separation with linear IgG and C3 at the basement membrane.
- Sjögren syndrome combines dry eyes, dry mouth, anti-Ro or anti-La antibodies and focal lymphocytic sialadenitis on lip biopsy.
- Pleomorphic adenoma is the commonest benign salivary tumour; mucoepidermoid carcinoma is the commonest malignant one.
Odontogenic lesions
- Ameloblastoma is typically a multilocular radiolucency in the posterior mandible of an adult; keratocyst is often multilocular with a high recurrence rate.
- Odontoma is the commonest odontogenic tumour and appears radiopaque; a dentigerous cyst surrounds the crown of an impacted tooth at the cementoenamel junction.
Radiographic interpretation
- Describe site, size, shape, margins (well or poorly defined, corticated), internal structure and effect on adjacent structures before naming a diagnosis.
- Apply ALARA: justify every exposure, use the smallest collimated field and choose intraoral views for fine detail; panoramic images blur the anterior region.
Worked example
A 25-year-old has a well-defined, corticated, unilocular radiolucency attached at the cementoenamel junction of an impacted 38. The description fits a dentigerous cyst; the plan is excision with histopathology because keratocyst and unicystic ameloblastoma can mimic it.
Traps
- Labelling every white patch leukoplakia without excluding frictional keratosis.
- Ignoring erythroplakia because it is asymptomatic.
- Naming a lesion before describing its margins.