Comparison of Bacteria Colonizing Dental Implants and Natural Teeth

Objectives: Dental implants are a widely accepted and highly predictable treatment modality in replacing natural teeth. Differences in the surface properties of dental implants compared to natural teeth suggest possible differences in the microbial composition of the biofilm forming on these surfaces and, ultimately, to infections around dental implants. This study compared the bacteria colonizing dental implants and natural teeth in the same subject. Materials and Methods: 83 subjects having at least one dental implant and one contralateral natural tooth were enrolled in the study. Bacterial samples obtained from the gingival sulcus around the dental implants and the natural teeth were assayed for; (1) total cell counts and the distribution of bacterial morphotypes by phase contrast microscopy; (2) the proportion of Gram positive and Gram-negative bacterial cells by light microscopy; and, (3) the presence and relative numbers of 14 different bacterial species by 16S rDNA hybridization. Results: The proportion of Gram positive and Gram negative cells was not significantly different between the natural teeth and the dental implants - 50.3% vs 47.9% Gram positive cells around natural teeth and dental implants, respectively. The total cell counts and the proportion of cocci, rods, fusiforms, and filaments were significantly higher (p<0.05) on the natural teeth. Of the 14 target bacterial species, Aggregatibacter actinomycetemcomitans, Capnocytophaga sp., Eubacterium saburreum, Porphyromonas gingivalis, Prevotella intermedia, Prevotella melaninogenica, Streptococcus mutans, and Tannerella forsythia were found in higher numbers around natural teeth compared to dental implants. Conclusions: The microbial composition of biofilms formed on natural teeth differs from the microbial composition of biofilms formed on dental implants. These differences are likely to have important implications for the pathogenesis of dental implant failure due to infections.