[Historical evolution and current research of the odontogenic focal theory]

Proposed in the early 20th century, the focal infection theory hypothesizes that teeth with dental caries, endodontic-periapical/periodontal diseases, plus impacted teeth and residual roots, might act as infection foci, inducing pathologies in distant organs including respiratory tract, gastrointestinal tract and brain, etc. During the prevalence of this theory, tooth extraction was well received as a key adjuvant therapy for systemic diseases, profoundly influencing paradigms of dentistry and clinical medicine. In the mid-20th century, advances in evidence-based medicine and diagnostic/therapeutic techniques led to the demise of focal infection theory. Tooth extraction ceased to be a major systemic disease intervention, while conservative dentistry as represented by root canal therapy progressed substantially. Since the proposal of "periodontal medicine" in the 1990s, the link between oral infectious diseases and systemic diseases has regained attention from dental and medical professionals. Recent progress in oral-systemic comorbidity animal models and high-throughput multi-omics has increasingly elucidated mechanisms by which oral infections exacerbate/induce systemic diseases. This article comprehensively reviews the historical evolution and impacts of focal infection theory on dental medicine (especially endodontics), offering references for future researches.