Longitudinal study of relations between human salivary antimicrobial proteins and measures of dental plaque accumulation and composition

Many studies have attempted to relate levels of antimicrobial proteins in saliva to oral health; results have been inconsistent, and one reason might be inconsistency of measures of plaque and saliva within subjects. This study investigated associations between plaque and salivary variables in longitudinal data. Whole saliva, and 8-h plaque pooled from buccal first permanent molars, was obtained from 32 dental students on Tuesdays from 3:00-6:00 p.m. over 4 weeks. Salivary flow rate was determined, and samples were assayed for lysozyme, lactoferrin, total peroxidase, myeloperoxidase, OSCN^-, sIgA and total protein. Colonies on mitis-salivarius agar were assigned to Streptococcus sanguis, Strep. mutans or Strep. salivarius on the basis of morphology, supplemented by the API Rapid Strep identification system. Consistency of values within subjects across weeks was evaluated by repeat-measures analysis of variance and intraclass correlation; data were transformed to reduce skewness. Pearson's r was used to determine associations between plaque and salivary variables. Significant intraclass correlations (α = 0.05) were found for all salivary variables except myeloperoxidase, and for total flora, total streptococci, Strep. sanguis and Strep. sanguis as a proportion of total streptococci. Significant Pearson correlations with Strep. sanguis as a proportion of total streptocci were found for total protein (r = -0.24), sIgA (r = -0.22), lactoferrin (r = -0.19) and OSCN^- (r = 0.20) when data from all weeks were pooled (n = 128). Strep. sanguis proportions tended to be low in subjects with high values for salivary proteins; the range of proportions was wider in subjects with low salivary values. These findings suggest some consistency of weekly values for many plaque and salivary variables. They also support previous cross-sectional data which suggested that salivary antimicrobial proteins may have some effect on plaque composition. This study was made before recent revisions in streptococcal taxonomy, and further research is needed to clarify interactions of salivary proteins with currently defined species.