Comparison of the Adhesive Remnant Index and Shear Bond Strength of Different Metal Bracket Bases on Artificially Aged Human Teeth: An In vitro Study

Aim: Bond failure can compromise the clinical efficacy and duration of orthodontic treatment. A decemented bracket can lengthen the course of treatment by about 0.6 months. This study aimed to compare the adhesive remnant index (ARI) and shear bond strength of different metal bracket bases on artificially aged human teeth. Materials and Methods: In this experimental in vitro, prospective, cross-sectional study, thirty-six human premolars were cemented with three types of metal bracket base designs: Group 1 had a laser-structured base, Group 2 had a mesh base, and Group 3 had a base with retention grooves. All groups were bonded with Transbond XT light-curing resin. Shear strength testing was performed, and the ARI was evaluated. The parametric one-factor analysis of variance test and Tukey's post hoc test were used for the comparison of shear bond strength, and the effect size was also evaluated with eta squared. In addition, the Kruskal-Wallis test was used to compare the ARI of the three groups on an ordinal scale. All statistics were set at a significance of P < 0.05. Results: The ARI scores did not exhibit any statistically significant differences (P = 0.163). Nevertheless, the three groups exhibited statistically significant differences in shear bond strength, with an effect size of 69% (P < 0.001). The mesh base bracket had the lowest average (9.9 ± 2.6 MPa) (P < 0.001), while the laser-structured base bracket had the greatest average (19.1 ± 3.0 MPa) (P = 0.006). Conclusion: The variation in shear bond strength was influenced by 69% due to the type of the metal bracket base used. Laser-structured and mesh-based brackets had the highest and lowest shear strength, respectively. All bases left a similar ARI on the tooth enamel.