Correlation between Periodontitis and Onset of Alzheimer's Disease: A Literature Review

Background: Alzheimer's disease is a slowly progressing neurodegenerative illness and the most common form of dementia. This pathology leads to an increase in cognitive decline and is responsible, in patients, for several difficulties in performing various activities of daily living, such as oral hygiene. Several experimental studies have shown that oral health in patients with Alzheimer's disease worsens in direct proportion to the progression of the disease due to the appearance of gingivitis and periodontitis. Methods: This clinical literature review aims to evaluate a possible correlation between periodontal disease and Alzheimer's disease, trying to understand if the periopathogens can contribute to the onset or the progression of Alzheimer's disease (AD). The study was conducted on the database PubMed (MEDLINE) of full-text systematic reviews in English on humans and animals that were published in the last five years, from 2018 to 2023. This returned 50 publications, which, once the eligibility criteria were applied, resulted in the 10 publications examined in this review. The selected articles were organized through the construction of tables, analyzed, and compared through Judith Garrard's Matrix method to arrive at the review results. Results: Infection by periopathogens can increase the risk of developing Alzheimer's disease, but also the onset of the latter can make it more difficult to maintain proper oral hygiene, favoring the onset of periodontal disease: it is possible to affirm the existence of a correlation between periodontitis and AD. It was found that patients exposed to chronic periodontitis have a greater risk of developing a cognitive decline or AD and that oral pathogens can be responsible for neuropathologies and increasing systemic inflammation. Conclusions: Periodontitis and periodontal pathogens represent a real risk factor for the onset or worsening of AD; however, the pathogenetic mechanism is still not completely clear.