Comparison of shear bond strength and enamel surface changing between the two‑step etching and primer and self‑etch primer methods in rebonding of orthodontic brackets: An in vitro study

Background: The aim of this study was to compare shear bond strength (SBS) and enamel surface changing of two methods of bonding in rebonding of orthodontic brackets. Materials and Methods: In this in vitro study, 30 human premolars were randomly classified into three equal groups. Two bonding systems were applied. At first bonding, Group 1 and 2 were bonded by conventional etching and primer technique (CEP) and Group 3 by self‑etching primer (SEP). Thermocycling for 5000 cycles was done. Then, 30 brackets were debonded and SBS and Adhesive remnant index (ARI) were evaluated. One sample was selected from each group, for SEM, 30 new brackets were used for rebonding. Group 1 was bonded by CEP method and Group 2 and 3 were bonded by SEP method. Thermocycling, SBS, ARI, and scanning electron microscope (SEM) were done in the same protocol of the first bonding. One‑way ANOVA, two‑sample t‑test, and Mann–Whitney U‑test were used for statistical analysis. P < 0.05 was considered statistically significant. Results: The mean SBS values were not significantly different between the three groups in the first bonding and rebonding stages (P = 0.22 and 0.24). Further, there was no significant difference between the first bonding and rebonding in SBS values of Groups 1, 2 and 3 (P = 0.44, P = 0.60, and P = 0.56). SEM examination showed obvious differences in the enamel surface between CEP and SEP samples in both first bonding and rebonding. Conclusion: With regard to the advantages of SEP methods, it seems this method can be properly used for rebonding of orthodontic brackets.