January - June

Objective: The purpose of this review is to address the purported association of periodontitis and the microbial pathogen, Porphyromonas gingivalis (P. gingivalis), with Alzheimer’s disease (AD). Methods: A scoping search was conducted using terms related to biological plausibility, comorbid associations of periodontitis, P. gingivalis and AD. Ovid Medline and PubMed were used to obtain abstracts which, in turn, were used to select papers for further evaluation. Special attention was given to articles addressing confounders, risk factors, and causality. A total of 113 papers from the basic science and medical literature and 48 papers from the dental literature, covering the years 2010 through May 2025 were reviewed. Results: Evidence exists showing that inflammation associated with periodontitis and P. gingivalis infection has implications for brain health. There is evidence to establish biologic plausibility for a microbial role in promoting neuroinflammation and neurodegeneration as seen in AD. Conclusion: There is evidence that both P. gingivalis and periodontitis satisfy the requirements of biological plausibility, have comorbid relationships, and may be risk factors for AD. However, there is insufficient evidence to establish P. gingivalis or periodontitis as independent causes of AD.