Objectives To characterize the interaction of 1-Ethyl-3-[3-dimethylaminopropyl] carbodiimide Hydrochloride (EDC) with dentin matrix and its effect on the resin-dentin bond. Methods Changes to the stiffness of demineralized dentin fragments treated with EDC/N-hydroxysuccinimide (NHS) in different solutions were evaluated at different time points. The resistance against enzymatic degradation was indirectly evaluated by ultimate tensile strength (UTS) test of demineralized dentin treated or not with EDC/NHS and subjected to collagenase digestion. Short- and long-term evaluations of the strength of resin-dentin interfaces treated with EDC/NHS for 1 hour were performed using microtensile bond strength (µTBS) test. All data (MPa) were individually analyzed using ANOVA and Tukey HSD tests (α=0.05). Results The different exposure times significantly increased the stiffness of dentin (p<0.0001, control - 5.15 and EDC/NHS - 29.50), while no differences were observed among the different solutions of EDC/NHS (p=0.063). Collagenase challenge did not affect the UTS values of EDC/NHS group (6.08) (p>0.05), while complete degradation was observed for the control group (p=0.0008, control - 20.84 and EDC/NHS - 43.15). EDC/NHS treatment did not significantly increase resin-dentin µTBS, but the values remained stable after 12 months water storage (p<0.05). Conclusions Biomimetic use of EDC/NHS to induce exogenous collagen cross-links resulted in increased mechanical properties and stability of dentin matrix and dentin-resin interfaces.

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The long-term maintenance of the surface quality of materials is fundamental to improving the longevity of esthetic restorations. In this manner, the use of surface sealants could be an important step in the restorative procedure using resin-based materials.

Based on the results, the splinting of pick-up impression copings is indicated for osseointegrated implant impressions. The square copings splinted with a prefabricated acrylic resin bar presented the best results among the pick-up impression techniques evaluated in this study.

The aim of this study was to evaluate the effect of different acidic solutions on the microhardness and surface roughness of restorative materials. The 120 specimens of restorative materials (Fuji II LC, Vitremer, Supreme XT, and Supreme XT + Biscover LV) were randomly divided into three groups according to the immersion media: hydrochloric acid, soft drink, or distilled water. Over a period of five weeks, the groups were immersed in the solutions, which were changed weekly. Data were tested using analysis of variance and the Fisher protected least significant difference test (p<0.05). The results showed that the glass ionomer materials showed the highest surface roughness values (Fuji II LC: 0.111 ± 0.014 μm before and 0.139 ± 0.016 μm after immersion; Vitremer: 0.177 ± 0.012 μm before and 0.084 ± 0.012 μm after immersion), whereas the lowest values were found for the resin sealed with Biscover LV before (0.047 ± 0.011 μm) and after exposure in distilled water (0.043 ± 0.007 μm), soft drink (0.040 ± 0.005 μm), and hydrochloric acid (0.045 ± 0.005 μm). The Supreme XT showed the highest microhardness values before (44.96 ± 2.51 KHN) and after the aging process (41.26 ± 1.22 KHN in water, 35.96 ± 0.81 KHN in soft drink, and 34.74 ± 0.97 KHN in HCl), with significant differences from the other materials (p<0.0001). The lowest microhardness values were found for glass ionomer materials. The solutions used in this study decreased the microhardness of all studied materials, whereas the sealed surface suffered minor changes in microhardness and surface roughness after exposure to acidic solutions.

Bleaching with either 10% carbamide peroxide or 35% hydrogen peroxide impairs the formation of the hybrid layer, resin tags, and bond strength. The use of sodium ascorbate following bleaching diminishes this adverse effect in the case of 10% carbamide peroxide but not so when 35% hydrogen peroxide is used as the bleaching agent. SUMMARYThe purpose of this study was to analyze the influence of 10% sodium ascorbate (SA) on the hybrid layer, resin tag length, and bond strength to dentin after bleaching. Six groups were tested: G C, control; G SA, sodium ascorbate (SA) + restoration; G CP, bleaching with carbamide peroxide (CP) + restoration; G CP+SA, bleaching with CP + SA+ restoration; G HP, bleaching with 35% hydrogen peroxide (HP) + restoration; and G HP+SA, HP + SA + restoration. After dental bleaching, the dentin was exposed and the antioxidant solution was applied to groups G SA, G CP+SA, and G HP+SA, before bonding procedures. The teeth were sectioned in the mesiodistal direction. One section was decalcified, and the specimens were embedded in paraffin and sectioned in the longitudinal direction with a thickness of 6 lm. Fifteen slices of each specimen were selected according to a systematic sample of slices with an interval proportional to the total number of slices obtained for each tooth. The specimens were stained using the Brown & Brenn method, and an optic microscope was used to analyze the hybrid layer thickness and resin tag length. The remaining tooth segment was sectioned into stick-shaped specimens and used for microtensile bond strength testing (0.5 mm/min). Statistical analysis was performed using two-way analysis of variance and Fisher test. The results for hybrid layer +

This study's aim was to evaluate the degradation rate of hydrogen peroxide (H2O2) and to quantify its penetration in tooth structure, considering the residence time of bleaching products on the dental enamel. For this study, bovine teeth were randomly divided according to the bleaching product received: Opalescence Xtra Boost 38%, White Gold Office 35%, Whiteness HP Blue 35%, Whiteness HP Maxx 35%, and Lase Peroxide Sensy 35%. To analyze the degradation of H2O2, the titration of bleaching agents with potassium permanganate was used, while the penetration of H2O2 was measured via spectrophotometric analysis of the acetate buffer solution, collected from the artificial pulp chamber. The analyses were performed immediately as well as 15 minutes, 30 minutes, and 45 minutes after product application. The data of degradation rate of H2O2 were submitted to analysis of variance (ANOVA) and Tukey tests, while ANOVA and Fisher tests were used for the quantification of H2O2, at the 5% level. The results showed that all products significantly reduced the concentration of H2O2 activates at the end of 45 minutes. It was also verified that the penetration of H2O2 was enhanced by increasing the residence time of the product on the tooth surface. It was concluded that the bleaching gels retained substantial concentrations of H2O2 after 45 minutes of application, and penetration of H2O2 in the dental structure is time-dependent.