[Physiology of the oral cavity. Dermatologic aspects].

The oral cavity is the first part of the digestive tract and, thus, the natural entry of food and fluids into the body. Further, it is permanently colonized by bacteria as are all other body surfaces. Humans have two sets of teeth: the deciduous dentition with 20 teeth and the permanent dentition with 32 teeth. Our teeth are unique solid bodies which penetrate the lining surface of the mouth. Thus special defense mechanisms are required to prevent the invasion of microorganisms into connective tissue and bone through the gap between the tooth surface and the gingiva. The host response is observed clinically as inflammation (gingivitis). In the conflict of microbiological exposure and host response this defense mechanism will derail in some individuals early and in most individuals later in life. The host's line of defense will yield to the microorganisms and the body will destroy the connective tissue and bone of the periodontal structures as part of its struggle against bacteria. Halitosis may indicate a particular medical problem (e.g. periodontitis). Contrary to common belief, in most cases halitosis is not due to gastric problems but is caused primarily by bacteria of the oral cavity.