Mouth is in direct contact with the outside world of the body and therefore abundant microflora sets there already in childhood. Even in a healthy mouth there is a plethora of bacteria, viruses and fungi. Oral microbial diseases usually arise from growth of opportunistic pathogens. Predisposing factors for oral infections are contact with pathogen carriers, impaired immune system, poor oral hygiene, and smoking. In chronic periodontitis tooth attachment is lost as a result of inflammation, and pockets formed between the tooth and gingiva. Chronic periodontitis is associated with an increased risk for cardiovascular diseases, pulmonary infections, and poor glycemic control of diabetes. This may be due to constant release of pathogenic bacteria and proinflammatory cytokines into the bloodstream.