Rampant interproximal caries in a smoker who chews mints

Correct answer: C. Continuous exposure to fermentable carbohydrate from the mints

• A. He is using fluoride toothpaste twice daily. Fluoride shifts the demineralisation-remineralisation balance, but it cannot compensate for a near-continuous acid challenge.
• B. He brushes twice daily, and brushing does not reach interproximal surfaces effectively in any case. Technique is not the governing variable here.
• C. CORRECT. What drives caries is not the QUANTITY of sugar but the FREQUENCY of exposure. A mint every twenty minutes keeps plaque pH below the critical value almost continuously, leaving no time for salivary buffering and remineralisation between challenges. Interproximal surfaces are the least self-cleansing and least accessible to a toothbrush, so they cavitate first — which is exactly the pattern seen.
• D. Smoking does reduce salivary flow and is an independent caries risk factor, but it does not explain why the lesions are specifically and uniformly interproximal. The mints do.

Note: Counsel on frequency, not just amount: swap to xylitol-containing or sugar-free mints, cluster any sugar intake with meals, add interproximal cleaning, and layer in high-concentration fluoride. Smoking cessation is a separate but linked conversation.

Correct answer: B. Physiological (racial) pigmentation

• A. Smoker's melanosis is real and is a genuine differential in this patient, but it is ACQUIRED and typically most marked on the anterior labial gingiva, appearing after the smoking habit begins. Pigmentation present for as long as he can remember is physiological.
• B. CORRECT. Physiological pigmentation is normal melanin deposition by melanocytes in the basal layer of the gingival epithelium. It is symmetrical, most pronounced on the attached gingiva, present from an early age, stable over time, asymptomatic and entirely benign. Its prevalence is highest in individuals with darker skin.
• C. Addisonian pigmentation is generalised and diffuse, affects the buccal mucosa and lips as well as the gingiva, is of RECENT onset, and comes with systemic features — fatigue, weight loss, hypotension, salt craving. This patient's pigmentation is lifelong and he has no systemic complaints.
• D. An amalgam tattoo is a FOCAL blue-grey macule adjacent to a restoration or an extraction site where metal fragments were embedded — not a symmetrical bilateral distribution across both arches.

Correct answer: B. Leukoedema

• A. Leukoplakia is a white patch that CANNOT be rubbed off or made to disappear by stretching, and is a diagnosis of exclusion with malignant potential requiring biopsy.
• B. CORRECT. Leukoedema is intracellular oedema of the spinous layer producing a diffuse, filmy, greyish-white appearance of the buccal mucosa. The defining diagnostic manoeuvre is that STRETCHING the mucosa makes it disappear. It is a benign variation of normal, more common in darker-skinned individuals and in smokers, and needs no treatment.
• C. White sponge nevus is an autosomal dominant condition producing thick, folded, spongy white plaques from childhood; it persists on stretching.
• D. Lichen planus presents with reticular Wickham's striae, bilateral and persistent, and does not vanish on stretching.