A cohort study on the association of early mutans streptococci colonisation and dental decay

In children, a strong relationship between the timing of colonisation of mutans streptococci (MS) and future caries risk has been shown to exist. The aim of the study was to examine the association of early MS colonisation with dental decay and the need for restorative treatment. The subjects had been participants in an earlier Finnish mother-child study and assumed to be high-caries-risk subjects due to their mothers' high MS levels. The information on MS colonisation at 2 years of age was available for 164 children. Of them, comprehensive data on dental health, visits and treatments until 10 years of age were found in the registers for 147 subjects. The children who had not been colonised by MS at 2 years of age (n = 118) maintained their teeth caries-free longer than the MS-colonised (n = 29) children. The median value for the caries-free time for MS-colonised children was 4.6 years, in comparison with 8.0 years for non-MS-colonised children (p < 0.001, hazard ratio 2.70; 95% CI 1.72-4.25, Cox regression). Until 10 years of age, the MS-colonised children had made on average 4.6 visits for restorative treatment, while the non-MS-colonised had made 2.8 visits (p = 0.005, Student's t test). The results suggest that the avoided early MS colonisation may lead to favourable long-term effects on caries experience and need for restorative treatment.