Limited Etching Time Increases Self-adhesive Resin Cement Adhesion to Enamel.

AIM: To evaluate the influence of different enamel etching times on the bond strength of two self-adhesive resin cements (RCs) with and without thermocycling (TMC). METHODS: One hundred twenty bovine teeth were used. Blocks of enamel (8×4×2mm) were obtained, polished, and randomly divided into two groups, according to the RC used: MaxCem Elite or RelyX U200. Groups were subdivided into four groups (n=16), according to the etching time: Control (0 seconds), 5 seconds, 10 seconds, and 20 seconds. Three RC cylinders (1-mm diameter) were built on each enamel block. The specimens were submitted to two storage conditions: 24 hours in distilled water or TMC (5000 cycles/5°C-55°C). Afterward, the specimens were submitted to the shear bond strength (SBS) test. The failure modes and adhesive interfaces were analyzed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Data were analyzed with three-way analysis of variance (ANOVA) and Tukey test (α=0.05). RESULTS: Etching increased the SBS for both the RCs,especially forthe groups etched for 5 and 10 seconds. TMC affected negatively the SBS of the control groups (p<0.05). No resin tags were observed in control groups, and the formation of tags was time dependent. CONCLUSION: The 10 seconds etching time was more effective in increasing the enamel-resin bond strength. TMC negatively affected bond strength in specimens without acid etching.

A new universal simplified adhesive: 18-month clinical evaluation.

PURPOSE: To evaluate the 18-month clinical performance of a multimode adhesive (Scotchbond Universal Adhesive, SU, 3M ESPE, St Paul, MN, USA) in noncarious cervical lesions (NCCLs) using two evaluation criteria. MATERIALS AND METHODS: Thirty-nine patients participated in this study. Two-hundred restorations were assigned to four groups: ERm, etch-and-rinse + moist dentin; ERd, etch-and-rinse + dry dentin; Set, selective enamel etching; and SE, self-etch. The composite resin, Filtek Supreme Ultra (3M ESPE), was placed incrementally. The restorations were evaluated at baseline, and at 18 months, using both the World Dental Federation (FDI) and the United States Public Health Service (USPHS) criteria. Statistical analyses were performed using Friedman repeated-measures analysis of variance by rank and McNemar test for significance in each pair (α=0.05). RESULTS: Five restorations (SE: 3; Set: 1; and ERm: 1) were lost after 18 months (p>0.05 for either criteria). Marginal staining occurred in four and 10% of the restorations evaluated (p>0.05), respectively, for USPHS and FDI criteria. Nine restorations were scored as bravo for marginal adaptation using the USPHS criteria and 38%, 40%, 36%, and 44% for groups ERm, ERd, Set, and SE, respectively, when the FDI criteria were applied (p>0.05). However, when semiquantitative scores (or SQUACE) for marginal adaptation were used, SE resulted in a significantly greater number of restorations, with more than 30% of the total length of the interface showing marginal discrepancy (28%) in comparison with the other groups (8%, 6%, and 8%, respectively, for ERm, ERd, and Set). CONCLUSIONS: The clinical retention of the multimode adhesive at 18 months does not depend on the bonding strategy. The only differences between strategies were found for the parameter marginal adaptation, for which the FDI criteria were more sensitive than the USPHS criteria.

Clinical effects of prolonged application time of an in-office bleaching gel.

OBJECTIVE: The aim of this study was to evaluate whether the use of a gel applied for 1 × 45 minutes would have the same bleaching rate and tooth sensitivity levels when compared with 3 × 15-minute applications. METHODS: In-office bleaching was performed in 30 participants with 35% hydrogen peroxide gel. In one group (n=15; 3 x 15 minutes), the bleaching agent was refreshed every 15 minutes, three times at each bleaching appointment. In the other group (n=15; 1 x 45 minutes) the gel was left undisturbed on the buccal surfaces of all teeth for 45 minutes at each bleaching appointment. This protocol was repeated after one week. The bleaching evaluation was completed by two blinded, calibrated evaluators who compared the baseline color of the maxillary anterior teeth with a value-oriented shade guide after each period. The patients recorded the tooth sensitivity on a 0-4 scale. The color changes were evaluated by appropriate tests (α=0.05). The percentage of patients with tooth sensitivity and its intensity were also statistically analyzed (α=0.05), respectively. RESULTS: The use of gel for a single 45-minute period (1 x 45 minutes) decreased the bleaching efficacy (p<0.05) 86.7%, and 100% of patients from the 3 × 15-minute and 1 × 45-minute groups, respectively, experienced tooth sensitivity (p=0.22). The intensity of sensitivity was lower for the 3 × 15-minute applications (p=0.04). CONCLUSIONS: A 35% hydrogen peroxide gel for in-office bleaching preferably should be applied in three 15-minute applications because 1 × 45 minutes reduces the bleaching speed and slightly increases the intensity of tooth sensitivity.