Objectives: Microbial flora and gingival conditions were compared between a group of patients with phenytoin-induced gingival hyperplasia as a test group, a control group of patients who were administered phenytoin without gingival hyperplasia and a blank group who took no phenytoin and no gingival hyperplasia in mentally retarded patients.
Materials and methods: Subgingival plaque samples were collected from a PHT-induced overgrown gingival pocket and microbiological experiments were performed by culture and PCR methods.
Results: The predominant genera in total cultivable bacteria from subgingival plaque samples were streptococcus and actinomyces with recovery ranges of 37.6-42.1% and 23.4-25.5% of total bacteria, respectively, in all groups. The test group showed a significantly higher level of obligate Gram-negative rods than the control and blank groups. Black-pigmented obligate anaerobic Gram-negative rods were detected in 10.3% of total cultivable bacteria in the test group. The black-pigmented rods were predominantly Prevotella intermedia in the test group and Prevotella nigrescens in the control and blank groups. Porphyromonas gingivalis and Porphyromonas endodontalis were also detected in the test group with small values.
Conclusions: These results suggested that black-pigmented rods, particularly P. intermedia, could be habitable in the environment of gingival hyperplasia.