The microbiota of periodontal and peri-implant niches

Abstract

Oral bacteria are the main etiological factor underlying peri-implant and periodontal diseases. Previous studies have found distinctively different microbial communities present in diseased peri-implant and periodontal niches, although some conserved putative pathogens have been identified. However, the differences between the microbiota of individual tooth/implant sites of differing clinical statuses, within the same oral cavity, remain poorly explored. Here, I investigated and compared the oral microbiota in peri-implant and periodontal niches in individuals presenting with both clinical conditions. I also investigated changes in the peri-implant microbiota after non-surgical treatment of peri-implant mucositis. In the first study, I employed a clone library-based approach, using newly-designed ‘Synergistetes-specific’ primer sets that respectively amplified the V2-V5 region of the 16S rRNA gene of oral cluster A and B Synergistetes taxa, within individuals possessing both non-diseased and diseased periodontal and peri-implant niches. My results demonstrated that the Synergistetes-specific primers sets were highly-effective at amplifying oral cluster A and cluster B Synergistetes taxa, respectively. Data indicated that there may be a complex, or more nuanced relationship between Synergistetes populations and the occurrence of peri-implant and periodontal diseases. In the second study, I used Illumina MiSeq sequencing of the hypervariable V3-V4 region of the 16S rRNA gene amplicons to characterize the subgingival/submucosal microbiota in non-diseased and diseased periodontal/peri-implant sites, within the same subject group. My results indicated that the microbial communities present within non-diseased and diseased tooth/implant sites in the same individual, share reasonably high levels of overall similarity. In the third study, I utilized an analogous Illumina MiSeq sequencing approach to compare supra-mucosal and submucosal bacterial communities present at peri-implant mucositis niches with their ‘counterparts’ around teeth, i.e. gingivitis niches, within individuals presenting with both clinical conditions. Results showed significant differences in the relative abundances of taxa present in subgingival versus sub-mucosal sites, and supra-gingival versus supra-mucosal sites, at all the taxonomic rank levels examined. These results suggested that the oral microbiota present around and within peri-implant mucositis niches differed significantly from those of gingivitis niches, within the same subject. In the last study, I used an analogous Illumina MiSeq sequencing approach to characterize the putative ‘microbial shift’ in peri-implant mucositis sites after non-surgical treatment. Shifts in the peri-implant microbiota occurred in both the healed (clinically-resolved) and unhealed (refractory) sites. Microbial differences were statistically significant only at the genus and species level. This mainly involved multiple Prevotella species; Porphyromonas endodontalis and Lachnoanaerobaculum sp. My results suggested that peri-implant mucositis disease status was associated with rather complex, often subtle, variations in the community structure of resident bacterial communities. Taken together, my results show that within individuals affected by both peri-implant and periodontal disease, the composition of the microbial communities present within the respective non-diseased and diseased niches may share many commonalities. However, there may also be notable differences in the respective taxa present within such sites. Furthermore, there may be significant alterations in sub-gingival and sub-mucosal microbial communities within healed and refractory sites, accompanying the treatment of peri-implant mucositis lesions.