A young male college student presents with worn incisal edges on his anterior teeth. The wear appears flat, smooth, and occurs on both the upper and lower teeth. What is the most likely cause?

Attrition is the mechanical loss of tooth structure resulting from tooth-to-tooth contact during mastication or parafunctional habits. It produces flat, smooth wear facets on occluding surfaces and incisal edges that match on opposing teeth. Bruxism (parafunctional grinding) is a common cause of attrition in young adults. Abrasion refers to wear from external mechanical agents (e.g., toothbrush abrasion), while erosion is caused by chemical dissolution from acids. Malocclusion may contribute to abnormal wear patterns but is not the primary cause of bilateral incisal wear. The correct term for this wear pattern involving tooth-to-tooth contact is attrition.