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 experim ental gingivitis was investigated in 25 non-dental students. Materials and Methods: Samples were taken from the dorsum of the tongue, th e tonsils (or tonsillar area), and the supra- and subgingival plaque. Results: The microbiological results show that 73% of the samples were posi tive for the bacterial species presumed to be Pi and/or Pn. In natural ging ivitis, gingival health and in experimental gingivitis 25, 23 and 25 subjec ts were found to be positive for Pi and/or Pn, respectively. The results of the 889 isolates that were succesfully purified and differentiated, show t hat almost all subjects were colonized with Pn whereas approximately half o f the study population harboured Pi. These 2 species were isolated from bot h dental plaque and mucosal sites and were found to colonize the oral cavit y simultaneously Conclusion: In natural gingivitis, at the start and after 14 days of experi mental gingivitis, Pn was the predominant micro-organism.