Gingival overgrowth frequently occurs in patients medicated with phenytoin (5,5-diphenylhydantoin) to control epileptic seizures. In a recent study, gingival overgrowth was observed in a patient in an experimental group evaluating an automatic toothbrushing system for severely disabled patients. During the evaluation period, which included an oral hygiene regimen provided by an attendant or housemate and a regimen with the Mississippi Dental Care System (MDCS), the patient's gingival overgrowth was noticeably reduced. The results of this study indicate that control of local factors with the MDCS is significantly better than the routine home care regimen, and that the phenytoin-associated gingival overgrowth in this patient was reduced by MDCS.