A patient on long-term phenytoin therapy for epilepsy presents to the dental office. What is the most likely oral manifestation associated with this medication?

Phenytoin (Dilantin) is an anticonvulsant associated with drug-induced gingival hyperplasia (gingival overgrowth) in approximately 30–50% of patients. The mechanism involves phenytoin stimulating gingival fibroblasts to overproduce collagen and reducing collagenase activity, leading to fibrous gingival enlargement. It typically begins in the interdental papillae and may eventually cover tooth surfaces. Good oral hygiene significantly reduces the severity of hyperplasia. Other drugs causing gingival hyperplasia include calcium channel blockers (nifedipine, amlodipine) and cyclosporine. Note: the original question (Q80) listed 'bleeding gums' as the answer — this is incorrect for phenytoin; gingival hyperplasia is the correct answer.