DOES VARIABILITY IN SALIVARY PROTEIN CONCENTRATIONS INFLUENCE ORAL MICROBIAL ECOLOGY AND ORAL HEALTH

Salivary protein interactions with oral microbes in vitro include aggr egation, adherence, cell-killing, inhibition of metabolism, and nutrit ion. Such interactions might be expected to influence oral ecology. Ho wever, inconsistent results have been obtained from in vivo tests of t he hypothesis that quantitative variation in salivary protein concentr ations will affect oral disease prevalence. Results may have been infl uenced by choices made during study design, including saliva source, s timulation status, control for flow rate, and assay methods. Salivary protein concentrations also may be subject to circadian variation. Val ues for saliva collected at the same time of day tend to remain consis tent within subjects, but events such as stress, inflammation, infecti on, menstruation, or pregnancy may induce short-term changes. Long-ter m factors such as aging, systemic disease, or medication likewise may influence salivary protein concentrations. Such sources of variation m ay increase the sample size needed to find statistically significant d ifferences. Clinical studies also must consider factors such as human population variation, strain and species differences in protein-microb e interactions, protein polymorphism, and synergistic or antagonistic interaction between proteins. Salivary proteins may form heterotypic c omplexes with unique effects, and different proteins may exert redunda nt effects. Patterns of protein-microbe interaction also may differ be tween oral sites. Future clinical studies must take those factors into account. Promising approaches might involve meta-analysis or multi-ce nter studies, retrospective and prospective longitudinal designs, shor t-term measurement of salivary protein effects, and consideration of i ndividual variation in multiple protein effects such as aggregation, a dherence, and cell-killing.