**1. Introduction**

The oral cavity (mouth) includes the lips, cheeks, palate (roof of the mouth), floor of the mouth, and the part of the tongue in the mouth (oral tongue). The oral cavity is important for food digestion and speech, the taste buds for sensing different tastes, and the mouth for breathing, drinking, facial expressions, and social interactions.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

It is now accepted that the improvement of oral environment leads to the enrichment of qual‐ ity of life. The number of healthy teeth in aged people well correlates with longevity. In Japan, many of Kampo medicines and component herb extracts have been applied to various oral diseases. However, the selection of Kampo medicines in each case is mostly depended on the experiences of attending physicians, due to the absence of a quantitative evaluation method of their efficacy. This urged us to establish the quick *in vitro* quantification method of antivi‐ ral, antitumor, anti‐inflammatory, and anti‐UV activity, using appropriate cultured cells [1]. These methods were applied to various Kampo medicines and component extracts of plants including licorice to clarify their relative potency.

It was the best to use oral cells for the study of oral diseases. Therefore, we used oral squa‐ mous cell carcinoma cell lines and normal oral cells for the study of antitumor activity, and human gingival and periodontal ligament fibroblasts for the study of anti‐inflammatory activity. However, we rather used nonoral cells for the study of antiviral and anti‐UV activity due to their higher sensitivity (T‐cell leukemia and Vero cells for HIV and HSV infection) and also considering the target specificity (skin cells for UV‐irradiation).
