Comparison of oral streptococci biofilm in caries-free and caries-affected preschool Mexican children.

Interaction of oral streptococci biofilm is the main etiological factor for dental caries. The aim of the study was to compare oral streptococci (OS) distribution in the biofilm of primary dentition from caries-free and caries-affected preschool Mexican children. This cross-sectional study involved 40 caries-free and 40 caries-affected children with primary dentition. Each child was examined using the dmfs index, DNA was extracted from saliva and presence of OS was determined by PCR. Data obtained showed no statistical difference regarding age and gender (P > 0.05). Streptococcus mutans (Smut), Streptococcus sobrinus (Ssob) and their combination showed significant statistical differences between groups (P < 0.05). Smut, Streptococcus sanguinis and Streptococcus gordonii had an inverse relation with dmfs index and Ssob had a direct relation similar to combined with Smut. Smut-Ssob combined with other OS showed statistical differences (P < 0.05). In free-caries group Streptococcus gordonii was more frequently identified than Smut. The ratio Smut/Streptococcus sanguinis could represent a high risk of dental caries development; this ratio was higher in the caries-affected (1.18) than in the caries-free group (0.32). In conclusion, OS play an important role in dental caries predisposition and severity, not only the presence of Smut and Srob, but also the complexity and distribution of OS in the biofilm.