Correlation between child caries incidence and S. mutans/ lactobacilli in saliva after correction for confounding factors

The correlation between caries incidence and Streptococcus mutans/ lactobacilli in saliva was studied in two different age groups, followed from ages 5 to 7 and from 12 to 14. The coefficients of correlation were computed before and after correction for the confounding effect of oral hygiene and the alternative bacteria. The best value for S. mutans was found for the total material in the younger age group (r = 0.24). For lactobacilli the best value was found for the total materials and in the subgroup with less favorable oral hygiene and S. mutans count in the older age group (r = 0.18). The connection between caries incidence and these bacteria was shown to be weak at the individual level, particularly after correction for confounding. The caries differences at group level between subgroups with less favorable and favorable counts of the bacteria were also checked after correction for confounders. The “reduction” figures for S. mutans varied between 23 and 63% and for lactobacilli between 8 and 37% in the two sets of material