Linking peri-implantitis to microbiome changes in affected implants, healthy implants, and saliva: a cross-sectional pilot study

<i>Mogibacterium timidum</i>, <i>Schaalia cardiffensis</i>, <i>Parvimonas micra</i>, <i>Filifactor alocis</i>, <i>Porphyromonas endodontalis</i>, <i>Porphyromonas gingivalis</i> and <i>Olsenella uli</i> were associated with the subgingival peri-implant biofilm. In contrast, Neisseria sp oral taxon 014, <i>Haemophilus parainfluenzae</i>, <i>Actinomyces naeslundii</i>, <i>Rothia mucilaginosa</i> and <i>Rothia aeria</i> were more prevalent in the healthy peri-implant biofilm. Functional pathways such as arginine and polyamine biosynthesis, including putrescine and citrulline biosynthesis, showed stronger correlations with PI-affected implants. In contrast, peri-implant health was characterized by the predominance of pathways involved in purine and pyrimidine deoxyribonucleotide de novo biosynthesis, glucose and glucose-1-phosphate degradation, and tetrapyrrole biosynthesis. Our findings reveal that healthy implants in PI-free oral cavities differ significantly in microbial composition and functional pathways compared to healthy implants co-occurring with PI-affected implants, which more closely resemble PI-associated profiles. This pattern extended to salivary samples, where microbial and functional biomarkers follow similar trends.