A patient shows erosion confined to the BUCCAL surfaces of the mandibular anterior teeth. What is the most likely cause?

Correct answer: B. An extrinsic dietary acid source, such as frequent citrus or acidic drinks

• A. Xerostomia is a powerful modifier — it removes buffering and clearance and accelerates any erosion — but it is not itself an acid source and does not produce a specific surface pattern.
• B. CORRECT. The DISTRIBUTION of erosion tells you its origin. EXTRINSIC acid — citrus, sodas, sports drinks, wine — first contacts the LABIAL/BUCCAL surfaces of the teeth, and habits such as swishing or sipping through the day concentrate it there. Lower anterior buccal erosion is therefore the extrinsic pattern.
• C. INTRINSIC acid from GORD or vomiting refluxes over the tongue and pools on the PALATAL surfaces of the MAXILLARY teeth and the occlusal surfaces of posterior teeth. It characteristically SPARES the lower labial surfaces, which the tongue protects.
• D. Statins are not erosive. Some medications are (chewable vitamin C, aspirin held in the sulcus, iron tonics), but statins are not among them.

Note: ⚠️ The source keyed gastroesophageal reflux. The classic teaching is palatal-maxillary for intrinsic acid and labial/buccal for extrinsic acid, so the described distribution argues for a dietary source. Good item for group discussion.