Dental caries and salivary level of cariogenic bacteria in schoolchildren

Methods: The study was conducted on 85 schoolchildren, 47 boys and 38 girls, born and living in a non-fluoridated area of Ho Chi Minh City. At baseline examination, the schoolchildren were divided into two groups: 30 children without caries and 55 with high caries. Dental caries were evaluated applying WHO criteria (1997) combined with ICDAS II for non-cavitated lesions. S.mutans and Lactobacilli levels were assessed using the CRT^® Bacteria test (Vivadent). The dental and bacteriological evaluations were done by three calibrated examiners (Kappa= 0.83) and re-conducted after one year. The correlation between caries increment and changes in cariogenic bacteria level was assessed by Fisher exact test, χ² test and logistic regression analysis. 

Results: After one year, as compared to caries free group, the percentage of children in high caries group that acquired at least one new lesion was significantly higher (17.5 times higher in deciduous teeth, 3.08 times higher in permanent teeth, p<0.05); the change of S.mutans level in high caries group was 1.25 times more (95% CI: 1.09-1.43, p<0.05). The children with increase of salivary S.mutans level developed new caries in permanent teeth 4.14 times (1.10-15.57) more than those without increase (p<0.05). The logistic regression analysis showed a strong association between caries increase and previous caries experience in both deciduous and permanent teeth, respectively 25.47 times (3.11-208.85) and 4.56 times (1.35-15.39).

Conclusions: There was a significant association between the increase of S.mutans level and caries increment among 8-9-year-old children, after one year. Previous caries experience was an important confounding factor in this relationship.