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Aim: To evaluate the shear bond strength of brackets bonded with resin-modified glass-ionomer cement (RMGIC) using various methods of enamel conditioning., Methods: Forty-five human premolars were randomly divided into five groups. The roots of these teeth were fixed in acrylic resin cylinders, and brackets were bonded to the teeth's crowns using the following material combinations: RMGIC only; RMGIC and corresponding primer; RMGIC, acid etching, and Scotchbond Multipurpose; RMGIC and two-step self-etching primer; and RMGIC and one-step primer. All specimens were submitted to pH cycling for 14 days before shear bond strength was assessed in a universal test machine., Results: The medians and standard deviations (in MPa) were RMGIC only = 8.34 ± 1.11; RMGIC and corresponding primer = 7.05 ± 2.24; RMGIC, acid etching, and Scotchbond Multipurpose = 7.00 ± 4.79; RMGIC and two-step self-etching primer = 0.54 ± 0.30; and RMGIC and one-step primer = 10.61 ± 4.58. The value for RMGIC and two-step self-etching primer was significantly lower than all other values., Conclusion: It can be concluded that the tested RMGIC is suitable for bonding orthodontic brackets, even when used by itself. Different enamel preparations do not improve its performance. However, they can worsen its bonding capacity as the combination with the two-step primer system clearly shows., (COPYRIGHT © 2009 BY QUINTESSENCE PUBLISHING CO, INC.)

Background: The authors conducted an in situ study of the influence of various time intervals after tooth bleaching with 35 percent hydrogen peroxide on the bond strength of resin-based composite restorations., Methods: After selecting 20 participants, the authors randomly fixed enamel and dentin blocks onto the buccal surfaces of posterior maxillary teeth one week before performing tooth bleaching with 35 percent hydrogen peroxide. After the bleaching treatment, they removed one block of dentin or enamel and prepared it for the bond strength tests according to these time intervals: no bleaching treatment (controls), immediately after bleaching, seven days after bleaching, 14 days after bleaching and 21 days after bleaching., Results: The analysis of variance and Tukey test showed significant differences between times (P<.05), and shear bond strength values of resin-based composite to enamel and dentin were lower immediately after the bleaching treatment., Conclusions: The authors found that 35 percent hydrogen peroxide reduces the bond strength to enamel and dentin and that it is necessary to wait seven days before performing adhesive restorative procedures., Clinical Implications: The results of this study suggest that clinicians should allow seven days to elapse after completion of in-office bleaching with 35 percent hydrogen peroxide before placing adhesive restorations.