The Role of Viruses in the Pathogenesis of Periodontitis.

Periodontitis is a multifactorial inflammatory disease, traditionally attributed to a bacterial biofilm. Increasing evidence indicates that viruses, especially members of the Herpesviridae family, are frequently detected in periodontal lesions and may influence disease onset and progression. This review provides an overview of viruses present in the oral cavity, including Herpesviridae, Papillomaviridae, Retroviridae, SARS-CoV-2, and emerging viral taxa such as Redondoviridae and bacteriophages, and summarizes their reported associations with periodontitis. Proposed mechanisms of viral contribution include modulation of local immune responses, facilitation of bacterial overgrowth, direct cytopathic effects on periodontal tissues, and synergistic interactions with classical periodontal pathobionts. Clinical correlations link viral load and co-infections with increased disease severity. Identification of direct causal relationships and therapeutic aspects, such as antiviral and combined antimicrobial approaches, is the subject of current research; however, clinical evidence remains limited. Overall, specific viruses show direct influence on periodontal bacterial pathogens and affect the host immune response, warranting further longitudinal and functional studies to clarify their exact role in periodontitis onset, progression, and treatment.