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.

Background: Periodontal disease is an inflammatory, chronic, and multifactorial disease. The objective of this study is to analyze the association between periodontal disease and some disorders such as papillomas (benign lesions), lichen planus (a chronic immune-mediated disorder), leukoplakia (potentially malignant lesions), and oral cancer (malignant lesions). Methods: For this study, 42 patients were recruited whose supragingival and subgingival plaque was qualitatively analyzed using a phase-contrast microscope, which allowed for the detection of compatible bacterial flora (immobile and composed mainly of cocci) indicative of periodontal health and incompatible bacterial flora (mobile and composed mainly of spirochetes) indicative of periodontal pathology. Patients with incompatible bacterial flora were then subjected to a laser-assisted periodontal treatment with irrigation with hydrogen peroxide within the periodontal pockets (a non-surgical laser-assisted periodontal protocol which is referred to as dye-free photodynamic therapy). Results: Based on the 42 patients recruited, there was no association between oral cavity lesions and periodontal pathogenic bacteria. Four of them were found to have incompatible bacterial flora. Indeed, it was found that almost all the patients had been previously instructed in the proper techniques of home oral hygiene, and more than half of them reported that they carried out periodic check-ups by a dental hygienist. Of the four patients with signs and symptoms of periodontitis, two stated a willingness to undergo the non-surgical laser-assisted periodontal protocol and showed improvements in periodontal indices such as CAL, PPD, and BoP. Conclusions: hygienists and dentists are determining factors in the prevention of periodontal disease and for the maintenance of good oral health.