Longevity of Bonding of Self-adhesive Resin Cement to Dentin.

OBJECTIVE: To evaluate the effect of root dentin treatment on the bonding of self-adhesive resin cement after 24 hours and after 6 months. METHODS: A total of 48 single-rooted premolars were endodontically treated and divided into four groups (n=12): Adper Scotchbond Multi-Purpose + RelyX ARC (ARC); RelyX U200 (U200); EDTA + RelyX U200 (EU200); and phosphoric acid (H3PO4) + RelyX U200 (HU200). After filling the roots, an Exacto No. 2 fiber post was cleaned, treated with silane (60 seconds), positioned, and light cured (LED; 60 seconds at 1200 mW/cm(2)). After storage (37°C/24 h), the roots were cut to obtain two discs (1 mm) of each third. They were stored in distilled water (24 hours at 37°C); one disc of each root-third was subjected to the push-out test (0.5 mm/min) at 24 hours and the other disc after six months of water storage (37°C). The data on the root-thirds were averaged for statistical purposes. The average values of bond strength (MPa) were analyzed by two-way analysis of variance and post hoc Student-Newman-Keuls (5%). RESULTS: There were statistical differences for the treatment of dentin (p<0.001), for time (p=0.003), and the interaction of treatment and time (p=0.017). After 24 hours, we observed lower bond strength in the HU200 group when compared with other groups (ARC, U200, and EU200). After six months, HU200 showed the lowest bond strength. Higher strengths were observed for EU200 and U200 similarly, which were higher than ARC. CONCLUSION: The bonding of the self-adhesive resin cement varied over time in the tested groups.

Influence of different photo-activation distances on cytotoxicity of a dental adhesive model resin.

AIM: This study evaluated the cytotoxicity of a dental bonding model resin (DBMR) submitted to different photo-activation distances. METHODS: A monomer mixture based on Bis-GMA and HEMA was used to assess the cytotoxicity in a mouse fibroblast-cell line. To promote different photo-activation distances glass slides were interposed between DBMR surface and halogen light curing unit (LCU) tip. Afterwards, the specimens were immersed in RPMI culture medium for 24 h to obtain extracts. The extracts were incubated in contact with the cells for 24 h. Finally, an MTT colorimetric assay was used to assess the cytotoxicity. The cell viability data (absorbance) were analyzed by one way ANOVA followed by Tukey's test (P<0.05). RESULTS: The light output decreased according to the increase in the number of glass slides between the halogen LCU tip and DBMR surface. Yet, the distance between the tip of the curing light system and the specimens had significant influence on the cytotoxicity. All extracts produced by groups submitted to different photo-activation distances showed cytotoxic effect after 24h of incubation. CONCLUSION: The photo-activation distance and the interposition of glass slides between LCU tip and DBMR was shown to play an important role in the cytotoxic effect.

Association of dental caries with HLA Class II allele in Brazilian adolescents.

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.