Periodontitis is a common chronic inflammatory disease, and oral health problems are frequent in people with Parkinson's disease (PD). Observational studies consistently indicate poorer periodontal status in PD, but evidence that periodontitis increases the incidence or progression of PD is inconsistent and does not establish causality. This narrative review summarizes current evidence on epidemiological associations, biologically plausible mechanisms, and dental management considerations. Human data support an association between PD and greater periodontal disease burden, plausibly related to motor impairment, reduced self-care capacity, salivary dysfunction, and altered oral microbial ecology. By contrast, proposed pathways from periodontitis to PD, including systemic inflammation, blood-brain barrier disruption, microbial products, and the oral-gut-brain axis, are supported mainly by preclinical, indirect, or low-level human evidence and should be regarded as hypotheses rather than established mechanisms. Observational reports of lower PD incidence among individuals receiving dental scaling do not demonstrate a preventive effect of periodontal treatment. In clinical practice, periodontal care should therefore be justified by established oral-health needs and individualized for PD-related motor, swallowing, cognitive, medication, and device-related considerations, rather than presented as a strategy to prevent or modify PD. Better longitudinal studies and interventional trials are needed to clarify temporality, mechanisms, and any neurological effects of periodontal treatment.
