Cup-shaped, shallow concavities on cusp tips and occlusal surfaces caused by chemical (acid) dissolution—without bacteria—are characteristic of:

Correct answer: A. Erosion

• A. Correct. Erosion is chemical loss of tooth structure (dietary/gastric acid) producing smooth, cupped (cupping) lesions and concavities.
• B. Abrasion is mechanical wear from a foreign object (e.g., toothbrush), classically notched/V-shaped at the cervical.
• C. Attrition is tooth-to-tooth wear (bruxism), producing flat matching facets.
• D. Abfraction is cervical loss attributed to occlusal flexure stress.