Unraveling the Microbial Mosaic and Inflammatory Core of Peri-implantitis

This study investigated the distinct microbiological and immunologic characteristics of peri-implantitis as compared with periodontitis. Both diseases are biofilm-driven inflammatory conditions affecting supportive tissues around teeth or implants, but their specific causes remain not fully understood. A cross-sectional study was carried out to compare the microbial profiles (i.e., composition and functional activity), the inflammatory mediators in crevicular fluid, and the potential impact of titanium particles in peri-implantitis. Twenty patients with moderate to severe periodontitis and 20 with peri-implantitis were included. Clinical assessments were performed, and biofilms were collected for 16S rRNA gene sequencing and metatranscriptomic analysis. Gingival crevicular fluid and peri-implant crevicular fluid were obtained to measure inflammatory markers and titanium levels (peri-implantitis group only). Results showed significant differences in microbial diversity between peri-implantitis and periodontitis. Specifically, peri-implantitis displayed enrichment of species such as Streptococcus parasanguinis , Streptococcus mutans , Cutibacterium acnes , and Aerococcus viridans . Additionally, the immune response in peri-implantitis appeared skewed toward a Th2/Th17 dominance. Analysis of the biofilm’s functional activity presented heightened expression of genes associated with flagella, bacterial chemotaxis, and various metabolic pathways in the peri-implantitis group. Interestingly, titanium levels modulate the overall microbial community structure, are associated with the abundance of certain peri-implantitis–associated species, and are positively correlated with Th17 levels in PICF. Peri-implantitis harbors distinct microbial communities and inflammatory patterns, potentially influenced by titanium particles. These findings suggest a unique environment driving tissue destruction in peri-implantitis as compared with periodontitis.