Comparative evaluation of the shear bond strength of ceramic brackets of three different base designs bonded to amalgam and composite restorations with different surface treatment

Background Nowadays, due to the increasing number of adult orthodontic applicants, who also have multiple dental restorations, it is important to have the ability to bond an orthodontic appliance to restoration surfaces. Objectives The aim of this paper was to determine the shear bond strength of ceramic brackets of 3 different base designs bonded to amalgam and composite restorations after using different surface treatment methods in vitro. Material and methods In an in vitro study, the surfaces of 180 amalgam and composite specimens were prepared by using sandblasting and the erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation. Ceramic brackets of 3 base designs, including Star, Cross and Slot, for upper central teeth were bonded to amalgam and composite surfaces by using Transbond™ XT Light Cure Adhesive. All specimens were incubated at a temperature of 37°C for 1 week, and then subjected to shear bond strength tests after 1,000 cycles of thermal cycling. The bond strength of the groups was analyzed by means of the one-way and two-way analysis of variance (ANOVA), and the comparison of the 2 groups was made with Tukey's test. Residual adhesives were also determined by a 4-part criterion (0-3) in different groups and the results were analyzed with the χ2 test. Results There was a significant difference in the shear bond strength of brackets of 3 base designs bonded to amalgam and composite surfaces with different surface treatment. Conclusions According to the results of this study, all surface treatment methods and different bracket base designs were able to provide sufficient shear bond strength on composite and amalgam surfaces. As far as the bracket base design is concerned, the use of each of the 3 base designs in the amalgam group brought desirable results in terms of the adhesive remnant index (ARI) and shear bond strength values; the use of the Star base design in the composite group proved to be suitable.