ABSTRACT
This chapter aims to review the current knowledge on the ecological considerations and microbial composition of various oral biofilm communities, and to elaborate their implication in the associated oral diseases. The oral cavity is the beginning of the digestive system and forms an intersection with the respiratory system. It is inhabited by a plethora of microorganisms that 70are collectively referred to as the 'oral microbiota' or the 'oral microbiome'. Microorganisms in nature tend to grow on surfaces, and only transiently exist in planktonic single cell form. In fact the most common oral diseases, including dental caries, endodontic infections, periodontal diseases and peri-implant diseases, are almost exclusively of microbial biofilm etiology. The dental plaque forming on the tooth surfaces is most often used synonymously with the terms 'dental biofilm' or 'oral biofilm'. Endodontic infections are clearly of polymicrobial nature, and the magnitude of the microbial load may be proportional to the extent of the periapical host response.
