Reactive oxygen species and dental health

Abstract

The microenvironments of the oral cavity are diverse and complex with respect to the tissues, physiological fluids, and microbiota. Consequently, the chemistry of the oral cavity is complex and in a state of flux that depends upon many factors that include the location, health (including state of inflammation), speciation of the microbiota (more than 1,000 species have been found in the oral cavity), the periodicity and nature of meals, the oral hygiene, and other environmental factors (including smoking habits). The aerobic supragingival space that is controlled by saliva and the anaerobic subgingival space that is controlled by gingival crevicular fluid are markedly different chemically, and this difference in chemistry has an effect on the types and amounts of reactive oxygen species (ROS) that are expected to be produced supragingivally and subgingivally. The ROS-generating microbiota that typically predominate in health are usually different than the pathogenic microbiota that displace commensal microbiota during pathogenesis, and the microbiota that generally thrive in aerobic environments are distinct from the anaerobic microbiota that are more sensitive to oxidative stress. ROS are derived from both the host and from infectious agents, but since such ROS are chemically identical independent of their origins, the sources of ROS in the oral cavity are generally subject to conjecture. Nonetheless, there has been considerable effort to correlate oxidative stress with disease through in vitro experiments and through epidemiological studies. This chapter focuses on the role of ROS in host defense within the oral cavity and on the effects of infectious agents on the production and consumption of ROS.