Dementia and, in particular, Alzheimer’s disease (AD), affects millions of people around the world and its prevalence is steadily rising annually. Some risk factors for AD, such as age, cannot be modified, while others could possibly be corrected. In recent years, many studies are tackling the problem of the oral and gut microbiota as a provoking factor for AD and other neurodegenerative diseases, but their relationship and specific pathophysiological mechanisms remain understudied. The microbiota of the oral cavity can be of particular importance due to the specificity of microorganisms and their localization, as well as the possibility of provoking neuroinflammation, which requires further study. This review covers the specific features of the oral microbiota, current views on the pathophysiological role of the oral microbiota in the development of AD, as well as the beneficial role of probiotics. The study of this issue can have an important practical application both for the early diagnosis of AD, and for its further treatment.