(2) The role of oral microbiota and intrinsic host factors in peri-implant health versus peri-implantitis – a pilot study

Introduction: Peri-implantitis is a mixed anaerobic infection dominated by gram negative bacteria. Studies have suggested a difference in bacterial composition in the sulcus surrounding the healthy and diseased peri-implant tissues .In addition, the cytokine profile of healthy implants is much different from diseased implants. Thus far, no unique microbial and inflammatory markers have been identified with peri-implantitis. The aim of this study is to characterize the role of oral microbiota in peri-implant health and disease by determining the composition of the oral bacteriome and mycobiome from subgingival dental plaque, cytokine profile in the crevicular fluid.

Methods: Gingival crevicular fluid and subgingival plaque samples were collected from 20 periodontally healthy patients with healthy implants and 9 periodontally healthy patients with peri-implantitis. Samples were also collected from a healthy tooth in each group. In addition, participants filled out a questionnaire regarding their general health, oral hygiene practices, and their taste perception. 8 cytokines were targeted and analyzed as follows: IL-1β, IFN-γ, IL-2, IL-4, IL-6, IL-8, IL-10, and TNF-α. 16S rRNA and ITS rRNA amplicon sequencing were performed to detect bacterial and fungal species.

Results: No statistically significant difference found in concentrations of IL-2, IL-8, IL-10, and TNF-α. However, statistically significant differences were observed for IL-4 and IL-6. The difference in concentration of IL-1 β between Group H Implant and Group P Implant approached significance. Alpha diversity analysis showed a significant difference between the groups H - Implant vs. P - Tooth and P - Implant vs. P - Tooth. Differential abundance analysis showed that many bacterial species were significantly enriched or depleted in implants with peri-implantitis compared to healthy implants. Significant differences in species abundances were also observed between the subgingival plaque of teeth from patients with peri-implantitis and from individuals with healthy peri-implant tissues Differential abundance analysis showed that Candida parapsilosis and Aspergillus restrictus were significantly enriched in the group of implants with peri-implantitis compared to healthy controls.

Conclusions: To the best of our knowledge, this is the first time Aspergillus restrictus is related to peri-implantitis. Moreover, we found that the relative abundance of Candida parapsilosis, but not Candida albicans , is significantly higher in peri-implantitis sites. This result can be attributed to different attachment mechanism of Candida parapsilosis. Since a significant difference was not seen between the beta diversity for 16S rRNA analysis of the subgingival plaque between the groups, our findings further challenge the concept that peri-implantitis is a bacterial disease with specific bacterial pathogens, and strengthens the idea that bacterial invasion happens secondary to bone loss as a result of not very well understood processes such as foreign body reaction.

Lead Author’s Contributions to the Research Project: The lead author was responsible for sample collection, data analysis, interpretation of the results, and composition of the abstract.