The purpose of this study was to evaluate the association between the frequencies of DR and DQ HLA class II alleles and the prevalence of dental caries in Brazilian adolescents. The study sample consisted of 164 adolescents aged 15– 19 years. For the assessment of caries experience the DMFT index was used, according to World Health Organization criteria. DNA samples of the adolescents were extracted from oral mucosa cells. The amplification of the alleles HLA-DR and HLA-DQ was carried out by polymerase chain reaction with sequence-specific primers (PCR-SSP). The products of PCR-SSP were electrophoresed and analyzed in agarose gel. Statistical analysis was performed using simple and multiple logistic regression to test the association between the adolescents’ caries experience and the presence of HLA-DR and -DQ alleles. Sociodemographic covariates were included in the model. The significance level for all analyses was p < 0.05. The prevalence of caries was 60.4% and the mean DMFT was 2.41 ± 2.53. Adolescents positive for HLA-DQ2 allele were less likely to have dental caries than their counterparts who were negative for this allele (OR = 0.33, CI 0.16–0.66), and those whose mothers presented low levels of education were 2.01 (CI 1.02–3.97) times more likely to have dental caries. There was no statistical difference between HLA-DR4, -DQ4, -DQ5, -DQ6 and dental caries. Our data provide evidence that genes within the MHC, especially the DQ2 group, may influence susceptibility to dental caries in Brazilian adolescents.
Silorane-based composite, an epoxy material, was marketed as promising less polymerization contraction than conventional restorative materials. The aim of this study was to evaluate, by means of photoelasticity, the polymerization stress generated by a silorane-based composite. Thirty photoelastic rings with orifices measuring 5 mm (d) × 3 mm (h) were prepared and divided into 6 groups (n = 5) according to the material tested. The inside walls of the rings were sandblasted with aluminum oxide, after which the restorative materials were inserted into the orifices and photoactivated according to the manufacturer's instructions. The specimens were analyzed and the visual representation of the stress was measured considering the isochromatic ring of first order. The data were converted to MPa and subjected to ANOVA and Tukey's test (α = 0.05). The adhesive Filtek P-90 (G5) showed high contraction stress (p < 0.05) when compared to G1, G2, G3, G4, and G6, which did not differ from each other (p > 0.05). The composite Filtek P-90 showed similar contraction stress compared to the conventional composite and, additionally, its adhesive showed higher stress than did the etch-and-rinse 2-step adhesive.
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