SEM Assessment of the Enamel Surface After Debonding of Ceramic Brackets

Objective: This study was conducted to compare the shear bond strengths, patterns of bond failure and enamel surfaces after debonding two ceramic brackets (ClearVu and Radiance Plus) and one standard metal bracket (Mini Uni-Twin). Background: Ceramic brackets are an esthetic alternative to metal brackets. The mean shear bond strength of ceramic brackets is significantly greater than for metal brackets. Excessive bond strength can result in pain upon debonding, damage to the bracket or permanent damage to the enamel including flaking, cracks or tooth fracture. Numerous studies have evaluated techniques to reduce the risk of enamel damage when debonding ceramic brackets, including the use of debonding pliers. Debonding pliers produce a concentrated stress within the adhesive, resulting in cohesive failures within the resin or adhesive failures outside the resin. Methods: A total of 75 caries-free extracted human premolar teeth were randomly divided into 3 groups: ClearVu ceramic bracket (TP Orthodontics, LaPorte, IN), Radiance Plus ceramic bracket (American Orthodontics, Sheboygan, WI) and Mini Uni-Twin metal bracket (3M Unitek, Monrovia, CA). The Instron Universal Testing Machine Model 8841 with a customized jig with a bracket removing plier was used to debond the brackets. The teeth were microscopically evaluated to determine the location of bond failure. Selected teeth were evaluated with the scanning electron microscope to evaluate for enamel cracks and tear-outs. Results: A one-way ANOVA was created and no significant differences in shear bond strength were discovered between the three groups. Using a chi-square test of independence it was determined that the brackets all possessed a different ARI score. After examining the standardized residuals, we found that Radiance Plus Ceramic bracket and ClearVu Ceramic bracket were both likely to have favorable bond failure patterns, compared to the Mini Uni-Twin Metal bracket. Radiance Plus was most likely to debond at the bracket-adhesive surface, with a majority or all of the adhesive on the tooth after debond. Teeth with unfavorable bond failure patterns (ARI score of 0 or 1) were evaluated with the scanning electron microscope. 11% of the total teeth in the study had enamel damage, including cracks and tear-outs. 62.5% of these teeth were from the ClearVu ceramic bracket group. Conclusions: Our results show that both Radiance Plus ceramic bracket and ClearVu ceramic brackets are comparable to the gold standard metal bracket used in this study, the Mini Uni-Twin, in terms of shear bond strength. Radiance Plus ceramic bracket had the most favorable bond failure pattern, but shattered more during debonding. ClearVu ceramic bracket had the most enamel damage when evaluated with the scanning electron microscope. American Orthodontics’ Radiance Plus Ceramic bracket is the recommended bracket of those studied