In a patient with a long history of self-induced vomiting, which surface is LEAST likely to show erosion?

Correct answer: C. Lingual surfaces of the mandibular anterior teeth

• A. The palatal surfaces of the maxillary anteriors are the FIRST and most severely affected site — the signature finding, called perimylolysis. Gastric contents wash directly across them.
• B. Palatal surfaces of the maxillary posteriors are affected as the erosion pattern extends distally from the anterior teeth.
• C. CORRECT. The lingual surfaces of the LOWER anterior teeth are the classically SPARED zone. Two things protect them: the tongue lies against them and physically shields them during regurgitation, and the submandibular and sublingual duct openings sit in the floor of the mouth, bathing that region in buffering saliva. This sparing is diagnostically useful — it is what distinguishes the pattern of intrinsic acid from generalised erosion caused by dietary acids.
• D. Maxillary posterior occlusal surfaces are commonly eroded, often showing restorations that stand proud of a dissolving occlusal table — 'raised amalgam islands'.

Note: The distribution is the diagnostic clue. Palatal maxillary erosion with sparing of the lower lingual surfaces points to intrinsic acid — vomiting or reflux. Diffuse erosion across all surfaces including the lower lingual points to extrinsic dietary acid. Note also that these patients should be advised NOT to brush immediately after vomiting; rinsing with water or a bicarbonate rinse comes first.