A patient on long-term phenytoin for seizure control is most likely to develop which oral side effect?

Phenytoin is a classic cause of drug-influenced gingival overgrowth, along with cyclosporine and calcium-channel blockers (e.g., nifedipine). Meticulous plaque control is key to prevention and management; severe cases may need gingivectomy.Other options: Black hairy tongue is linked to tobacco/antibiotics/poor hygiene; phenytoin does not cause enamel hypoplasia of erupted teeth or intrinsic staining like tetracycline.Key exam takeaway: Phenytoin, cyclosporine, and calcium-channel blockers cause gingival overgrowth; plaque control is the mainstay.