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In restorative dentistry, the use of composite resins with direct technique for the replacement of missing tooth structure is very common. One drawback is that surface roughness allows the adherence of microorganisms and the formation of dental plaque, being the polishing technique a key stage in the restoration process. The aim of this paper is to review the process of bacterial colonization of composite resins used with direct technique. According to in vitro studies, bacterial adhesion on microhybrid composite resins is 3.91 ± 0.52 UFC and on nanohybrid is 3.34 ± 0.74 UFC. Resins with particle size of 2.5 micrometers contained a greater volume of biofilms and enabled adhesion of S. mutans; in turn, resins with particle size of 0.1 to 0.4 micrometers showed lower bacterial adherence. As summary, the degree of bacterial colonization depends on hygiene, polishing technique and composition of restorative material: the bigger the particle size, the greater the adhesion of bacterial plaque.

Dental caries is a multifactorial, infectious and communicable disease, and Streptococcus mutans is the key microorganism related to this pathology. The objective of this study was to evaluate the association between the levels of Streptococcus mutans and caries in schoolchildren. Descriptive, cross-sectional study conducted on 100 schoolchildren aged 6 to 10 years from the Unidad Educativa Checa Cuenca, Ecuador. ICDAS index and odontogram were used to measure the prevalence and severity of caries. For the identification and quantification of Streptococcus mutans , dental plaque samples were used for cultivation and biochemical tests (MicroScan). The results were analyzed statistically using absolute and relative frequencies, for bivariate analysis Chi-squared test and Fisher’s Test ( p <0.05) were used. 96% of the schoolchildren presented dental caries, 69% of them were children aged 8 to 10 years, the prevalence of caries was higher in females reaching 57%. High (60,000UFC/ml) and very high (70,000UFC/ml) levels of Streptococcus mutans were found on schoolchildren aged 8 to 10 years reaching 22% and 8%, respectively ( p =0.005). Regarding sex, high (60,000UFC/ml) as well as very low (0- 20,000UFC/ml) levels of Streptococcus mutans appeared without difference by sex ( p = 0.355). Schoolchildren without caries presented a low count of Streptococcus mutans (0 -20,000 UFC/ml), children with caries presented variable levels of Streptococcus mutans , although higher than 20,000UFC/ml ( p <0.001). Conclusion: there is a high prevalence of caries in the school population with high levels of Streptococcus mutans.