Correlation of Enamel Caries with Occlusal Surface Biofilm: A Quantitative Analysis of Streptococcus mutans, Slackia exigua, and Corynebacterium matruchotii

Aims To detect S. mutans, S. exigua and C. matruchotii amounts in biofilm from occlusal surfaces of first permanent molars categorized by two clinical diagnostic tools which are the Visible Occlusal Plaque Index (VOPI) and the International Caries Detection and Assessment System (ICDAS) and to assess the correlation between levels of bacterial and enamel caries on occlusal surfaces. Study design Plaque samples were obtained from 160 Thai children (6–8 years-old) and assigned to four groups (n = 40 per group) based on VOPI and ICDAS scores. Methods DNA was extracted and analyzed using real-time PCR quantitatively and specific primers targeting total bacteria (BAC16S), S. mutans, S. exigua , and C. matruchotii. Results Children’s ages were different among the VOPI groups (p<0.001). Quantities of BAC16S, S. mutans and S. exigua, increased significantly with higher VOPI scores (p<0.001). C. matruchotii showed a declining trend when VOPI scores increased. It was detected at 97.5%, 82.5%, 70% and 47.5% in VOPI 0, 1, 2, and 3 groups, respectively. A difference between ICDAS and VOPI scores (p<0.001) was showed. There were positive correlations between VOPI and BAC16S (r =0.504, p<0.001), ICDAS and BAC16S (r = 0.506, p < 0.001), and S . mutans and BAC16S (r = 0.583, p < 0.001). S. mutans /total bacteria and S. exigua /total bacteria ratios exhibited associations (p < 0.001). Using logistic regression, subjects scoring in the VOPI 1, 2, and 3 groups had a 1.97, 3.99, and 6.05 higher chance of having enamel caries compared to those subjects in the VOPI 0 group, respectively. Conclusion Quantities of S. mutans and S. exigua escalated with higher VOPI scores, and associated with greater enamel caries, while C. matruchotii decreased. The inverse relationship between C. matruchotii and VOPI suggests its potential indicator for caries-free or good oral health status.