The link between periodontitis and Alzheimer's disease – emerging clinical evidence

Alzheimer's disease (AD) is one of the most prevalent progressive neurodegenerative disorders and among the leading causes of mortality globally. AD is characterized by continued cognitive and behavioral impairments associated with memory loss, difficulty with reasoning, and language impairment. In parallel, periodontal disease (PD) is a prevalent chronic disease, affecting one in two adults, with associations to various systemic disease. Recently, pre-clinical and clinical studies have elucidated associations between PD and AD. The most recent evidence suggests a bi-directional relationship between both disease entities. However, a causal relationship between PD and AD has yet to be established. In this review, we aim to provide an overview of the pathogenesis of PD and AD, and present the main theories behind the link between PD and AD, the role of periodontal pathogenic bacteria on the onset and progression of AD, and emerging clinical evidence on the relationship between PD and AD.