RÉSUMÉ
Nifedipine [Adalat], used in treatment of cardiovascular disorders, has been found to cause gingival enlargement as one of its side effects. Phenytoin [Epanutin] was used in this study as positive control as gingival hyperplasia is one of its well known side effects. The present study was carried out on one hundred and twenty-five male albino rats. They were divided into three groups: Group I was used as control, group II was divided ito subgroups A and B which received the high and low therapeutic doses of phenytoin respectively while group III was divided into subgroups A and B which received the high and low therapeutic doses of nifedipine respectively. All drugs were introduced by orogastrie tubes daily for a period of 5 weeks. Histopathological studies were performed on the gingiva using haematoxylin and eosin, Van Gieson and Mallory's aniline blue stains. The present study showed that both nifedipine and phenytoin produced microscopic gingival hyperplastie changes in rats in the form of fibroplasia and increased collagen density. Nifedipine-induced hyperplasia was not dose-dependent. while phenytoin-induced hyperplasia was dose-dependent. Also the degree of hyperplasia in both drugs was directly related to the duration of therapy beginning as early as three weeks