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Figure 2. Annual publication trends in research on the association between periodontitis and PD (2015-2025). The x-axis represents publication year, and the y-axis represents the number of publications identified for each year. The overall upward trend indicates increasing academic interest in the relationship between periodontitis and PD, especially in relation to the oral-brain axis, neuroinflammation, and periodontal pathogen-driven neurodegeneration. A marked rise in publication output was observed after 2020, with a peak in 2025. Publications were identified through database searches of PubMed, Web of Science, CNKI, Wanfang, and VIP using combinations of the keywords “PD”, “oral health”, “dental caries”, and “periodontitis” for the period from 2015 to 2025. Inclusion criteria were articles published within the predefined time window; studies focusing on PD and periodontitis/oral health; and epidemiological, clinical, experimental, mechanistic, and review articles relevant to the interaction between periodontitis and PD. Exclusion criteria were duplicate records; studies unrelated to PD or periodontitis; conference abstracts without sufficient bibliographic information; editorials, news items, or letters lacking substantive scientific content; and articles with inaccessible or inadequate full-text information for evaluation. PD: Parkinson’s disease; CNKI: China National Knowledge Infrastructure; VIP: Chinese Science and Technology Journal Database.