**2. Oral health**

The mouth has a varied and heterogeneous microbial community. Oral health can be a state of being free from chronic mouth and tooth pain, such as oral and throat cancer, tooth loss, periodontal disease, and the other diseases that affect this tissue. The etiology of periodontal diseases and caries shows the prevalence of these both having microbial components. Host microbiota has important role in the individual's health. The theory from Nobel laureate Ilya Metchnikoff says "we fight microbe with microbe" and has attracted numerous followers [10].
