Critical Reviews in Oral Biology & Medicine, Vol 6, 343-367, Copyright © 1995 by International & American Associations for Dental Research
Does variability in salivary protein concentrations influence oral microbial ecology and oral health?
J. D. Rudney
Department of Oral Science, School of Dentistry, University of Minnesota, Minneapolis 55455, USA.
Salivary protein interactions with oral microbes in vitro include
aggregation, adherence, cell-killing, inhibition of metabolism, and
nutrition. Such interactions might be expected to influence oral ecology.
However, inconsistent results have been obtained from in vivo tests of the
hypothesis that quantitative variation in salivary protein concentrations
will affect oral disease prevalence. Results may have been influenced by
choices made during study design, including saliva source, stimulation
status, control for flow rate, and assay methods. Salivary protein
concentrations also may be subject to circadian variation. Values for
saliva collected at the same time of day tend to remain consistent within
subjects, but events such as stress, inflammation, infection, menstruation,
or pregnancy may induce short-term changes. Long-term factors such as
aging, systemic disease, or medication likewise may influence salivary
protein concentrations. Such sources of variation may increase the sample
size needed to find statistically significant differences. Clinical studies
also must consider factors such as human population variation, strain and
species differences in protein-microbe interactions, protein polymorphism,
and synergistic or antagonistic interaction between proteins. Salivary
proteins may form heterotypic complexes with unique effects, and different
proteins may exert redundant effects. Patterns of protein-microbe
interaction also may differ between oral sites. Future clinical studies
must take those factors into account. Promising approaches might involve
meta-analysis or multi-center studies, retrospective and prospective
longitudinal designs, short-term measurement of salivary protein effects,
and consideration of individual variation in multiple protein effects such
as aggregation, adherence, and cell-killing.