Chapter 8

INSIGHT: Biofilm is composed of microorganisms attached to a surface embedded with extracellular matrix molecules and nutrients. From an ecologic viewpoint, the oral cavity, which communicates with the pharynx, should be considered as an “open growth system” with an uninterrupted ingestion and removal of microorganisms and their nutrients. The colonization of the oral cavity also starts close to the time of birth. Within hours after birth, the sterile oral cavity will be colonized by low numbers of mainly facultative and aerobic bacteria. At that time, the oral microbiota of newborns closely resembles the mother’s vaginal microbiota or, for newborns delivered by cesarean section, the mother’s skin microbiota. From the second day, anaerobic bacteria can be detected in the infant’s edentulous mouth. The number of oral bacteria increases gradually as a result of exposure to external environmental microbial sources. Streptococcus salivarius and Streptococcus mitis have been identified among the first and most dominant oral microbes to colonize the oral cavity of newborn infants. After tooth eruption, a more complex oral microbiota is established that includes Streptococcus sanguinis and Actinomyces odontolyticus .

Clinical Consideration: More than 600 different species are capable of colonizing the adult mouth. Most of the oral bacteria are harmless commensals under normal circumstances, but under specific conditions, some species my be associated with disease. The importance of the commensal microbiota in establishing and maintaining homeostasis in the oral cavity is clearly illustrated by the development of yeast infections that occur when the normal oral microbiota is altered, such as after a longer period of systemic antibiotic usage.

Please see TRENDS featured news articles about peri-implantitis and local delivery of antibiotics demonstrating the role of pathogenic biofilm to both tooth and implant surfaces.