Microbial dysbiosis and immune dysregulation in periodontitis and peri-implantitis

Periodontitis and peri-implantitis are chronic inflammatory diseases which are primarily driven by excessive and dysregulated immune responses. This would result in irreversible tissue destruction around teeth and implants. Although the microbiome serves as an initiator of inflammation and leads to microbial dysbiosis, persistent and unresolved inflammation is the primary driver of tissue and bone loss. These conditions result from a dynamic interplay between the host immune response and pathogenic biofilms. Microbial dysbiosis results from a shift from a eubiotic (symbiotic) oral microbiome to a dysbiotic microbial community. This is initiated by excessive inflammation and manipulates host immunity to promote chronic inflammation. Concurrently, immune dysregulation, including imbalances in innate and adaptive immune responses that result from a failure of resolution of inflammation pathways, exacerbates tissue destruction through the overproduction of pro-inflammatory cytokines and the activation of destructive pathways, such as neutrophil-mediated degradation and osteoclast activation. This review explores the mechanisms underlying microbial dysbiosis and immune dysregulation in periodontitis and peri-implantitis, emphasizing their contribution to inflammation, bone resorption, and disease progression.