Alzheimer's disease (AD) affects approximately 5.3 million people in the U.S. and this number will increase as the population ages and the life-span increases. Therefore, of paramount importance is identifying mechanisms and factors that affect the risk of developing AD. The etiology and pathogenic mechanisms for AD have not been defined, although inflammation within the brain is thought to play a significant role. Consistent with this hypothesis, studies suggest that peripheral inflammations, dysbiotic conditions, and infections contribute to the inflammatory state of the brain and may constitute risks for AD. Recently, several peripheral conditions with an inflammatory basis such as diabetes and obesity have been recognized as risks for AD. Periodontitis is a prevalent, chronic peripheral polymicrobial disease associated with gram negative, anaerobic bacteria, which exhibits significant localized and systemic inflammatory effects. This review will present evidence suggesting that periodontal disease may also be a risk factor for AD and possible mechanistic links between periodontitis related inflammation and AD. It will review the pathogenesis of periodontitis and the mechanisms by which periodontal infections may affect the onset and progression of AD. Periodontitis is a treatable condition and may be a readily modifiable risk factor for AD. Therefore, further studies including intervention trials are warranted.