9.1.1. Cardiovascular Disease

CVD is a general term for atherosclerotic diseases, and atherosclerotic CVD is one of the leading causes of death in the world [100]. Generally, circulating leukocytes in the blood vessels do not adhere to the endothelium under normal conditions. However, when an inflammatory response occurs, various adhesion molecules, such as vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), and P-selectin, are expressed in the endothelial cells, inducing the adhesion of leukocytes [101]. When leukocytes adhere to the endothelium, they migrate into the intima, and diapedesis occurs via the expression of matrix metalloproteinases [102]. Several studies regarding the link between periodontitis and CVD have reported their positive association [100,105,106]. Several risk factors including smoking, diabetes, hypertension, and hypercholesterolemia have been focused on as the contributory factors in atherosclerosis; however, recent studies have suggested that immune and inflammatory mechanisms caused by oral bacteria could be an important factor in atherosclerosis [103,104]. Oral bacteria, such as periodontal and cariogenic pathogens, are known as etiological factors in the development of atherosclerosis, which is the first step of CVD. To investigate the association between oral microbiomes and atherosclerosis, several studies have been performed examining atheromatous lesions with various molecular biologic techniques. Fundamentally, periodontal pathogens were cultured in atheromatous plaque [105], and fluorescence in situ hybridization [106], DNA– DNA hybridization [107], and real-time PCR [108] results showed the presence of oral pathogens in atheromatous lesions. Based on these results, oral microbiome studies have been widely conducted on oral bacteria-induced atherosclerotic CVD (Table 2).




**Table 2.** *Cont.*
