Alzheimer’s

disease (AD) has been increasingly associated with poor oral health,

including periodontal disease, tooth loss, and oral dysbiosis. This

review summarizes current evidence linking oral health and AD, with

an emphasis on oral pathogens, systemic inflammation, and cognitive

decline. A literature review conducted up to June 30, 2025,

identified 20 eligible studies. Individuals with AD consistently

showed oral dysbiosis, characterized by increased levels of

Porphyromonas gingivalis,

Fusobacterium nucleatum,

and Tannerella forsythia,

and decreased levels of commensals such as Streptococcus

and Rothia. Periodontitis and tooth loss were independently

associated with greater AD risk. A large cohort study of over 32.6

million individuals reported more than a twofold increased AD

risk among those with poor oral health. These findings support the

potential role of oral hygiene as a modifiable and

cost-effective preventive strategy against AD.