Salivary levels of mutans streptococci associated with restorations: a case-control study

Our aim was to estimate whether restorative therapy with amalgam and composite resin could decrease salivary mutans streptococcal level, thus also decreasing the risk for other caries development. We selected a case group of 93 children with detectable salivary mutans levels (i.e., at least 1x10(4) cfu/ml), and a control group (n=93 subjects) with undetectable levels. Children had the same age (12 years), no extracted teeth, crowns, temporary fillings, and restorations other than amalgam and composite resin, and the two groups had similar gender distribution. We clinically examined children and recorded active caries, restorations and oral hygiene level by means of gingival bleeding on probing; we also investigated sucrose intake at breakfast. The case group had statistically significant higher prevalence of restorations (36.6% vs. 18.3%), active caries (44.1% vs. 12.9%), and bad oral hygiene (84.9% vs. 68.8%) than the control group. However, the logistic regression analysis showed that presence of active caries was the only significant variable associated with mutans streptococci (OR=4.0; p=0.0002), while the effects of sucrose intake and of restorations were marginally significant. This apparent contrast between statistical analyses was due to the concomitant presence, in children with detectable mutans streptococci level, of restorations and decayed teeth at the same time, and, on the basis of the multivariate analysis, presence of mutans streptococci in these children was explained by the presence of active caries, more than restorations.