Occurrence of Prevotella intermedia and Prevotella nigrescens in relation to gingivitis and gingival health

Aim: The occurrence of Prevotella intermedia (Pi) and Prevotella nigrescens (Pn) in relation to natural gingivitis, gingival health and 14-day experimental gingivitis was investigated in 25 non-dental students. Materials and Methods: Samples were taken from the dorsum of the tongue, the tonsils (or tonsillar area), and the supra- and subgingival plaque. Results: The microbiological results show that 73% of the samples were positive for the bacterial species presumed to be Pi and/or Pn. In natural gingivitis, gingival health and in experimental gingivitis 25, 23 and 25 subjects were found to be positive for Pi and/or Pn, respectively. The results of the 889 isolates that were succesfully purified and differentiated, show that almost all subjects were colonized with Pn whereas approximately half of the study population harboured Pi. These 2 species were isolated from both dental plaque and mucosal sites and were found to colonize the oral cavity simultaneously Conclusion: In natural gingivitis, at the start and after 14 days of experimental gingivitis, Pn was the predominant micro-organism.