Longitudinal analysis of the association of human salivary antimicrobial agents with caries increment and cariogenic micro-organisms: a two-year cohort study.

Previous studies of the possible associations of salivary antimicrobial agents with dental caries have given controversial results, obviously mainly because almost all studies have been cross-sectional. Our aim was to find out, in a two-year longitudinal follow-up study, the associations among selected salivary non-immune and immune antimicrobial variables, cariogenic bacteria, and caries increment. The study population was comprised of 63 subjects, all of whom had their 13th birthday during the first study year. In addition to a comprehensive dental examination at baseline and after 2 yrs, paraffin-stimulated whole saliva samples were collected in a standardized way at six-month intervals. Saliva samples were analyzed for flow rate, buffer effect, lysozyme, lactoferrin, total peroxidase activity, hypothiocyanite, thiocyanate, agglutination rate, and total and specific anti-S. mutans IgA and IgG, as well as for numbers of total and mutans streptococci, lactobacilli, and total anaerobic bacteria. Cluster analysis and Spearman-Rank correlation coefficients were used to explore possible associations between and among the studied variables. During the two-year period, a statistically significant increase was observed in flow rate, thiocyanate, agglutination rate, anti-S. mutans IgA antibodies, lactobacilli, and total anaerobes, whereas lysozyme, lactoferrin, and total and anti-S. mutans IgG antibodies declined significantly. Based on various analyses, it can be concluded that, at baseline, total IgG and hypothiocyanite had an inverse relationship with subsequent two-year caries increment, anti-S. mutans IgG antibodies increased with caries development, and mutans streptococci and lactobacilli correlated positively with both baseline caries and caries increment. Total anaerobic microflora was consistently more abundant among caries-free individuals. In spite of the above associations, we conclude that none of the single antimicrobial agents as such has sufficiently strong power to have diagnostic significance in vivo with respect to future caries.