Phenytoin-induced gingival overgrowth is a well-known and frequently reported gingival lesion, which was first detected in 1939. However, there are conflicts in the literature about the agents which affect the severity of the lesion. Un-cooperative dental patients are one of the most unsuccessfully treated periodontal patient groups because of the difficulty in maintaining their oral hygiene. This case report consists of two cases with the same characteristics: phenytoin usage, comprehension and speech defects and poor oral hygiene, but each case differs in the duration of the phenytoin therapy. Both of the cases received scaling, root planning and a gingivectomy.