**2. The potential pathogenicity of dental plaque as oral biofilm**

Oral plaque contains also dental caries and periodontal disease causing organisms [9–12], and when these exert their potential pathogenicity, they are considered to accelerate biofilm formation even more. Generally it can be said that with increasing thickness of the biofilm, the bacterial metabolites build up at the bottom of the biofilm, and the caries and periodontitis occurrence proliferate.

Caries and periodontal diseases are called the two major dental diseases, and both of them occur as oral infectious diseases which are caused by specific bacteria known as cariogenic bacteria (such as *Streptococcus mutans*) and periodontal pathogens (such as *Porphyromonas gingivalis*) growing in plaque. This status is interpreted as dysbiosis of the oral flora. In addition, a small number of fungal genus *Candida* is also present in the indigenous oral resident microflora, and some factors also cause its growth in the plaque, resulting in dysbiosis, which causes a major oral mucosal disease, oral candidiasis. However, there is currently no technique to selectively eliminate only those causative microorganisms from the flora.
