Repeated bracket bonding: Conventional or self-etching primer?

Background: The aim of this study was to evaluate the effects of repeated bonding using a conventional primer (CP) or a self-etching primer (SEP) on the in vitro shear bond strength (SBS) and adhesive remnant index (ARI) of orthodontic brackets. Methods: A total of 144 human premolars were divided into two equal-sized groups and bonded with metal brackets using a CP in one group and an SEP in the other group. The SBS and ARI were determined after bracket debonding using a universal testing machine. Each group of premolars was then further divided into two equal-sized subgroups, which were bonded with new brackets using a CP in one subgroup and an SEP in the other subgroup. Again, the SBS and ARI were determined. Differences in SBS and ARI between the groups and among the subgroups were tested for statistical significance. Results: During the first debonding sequence, the mean SBS values were 10.60 and 10.13 MPa in the CP and SEP groups, respectively. During the second debonding sequence, the mean SBS values ranged from 10.37 to 11.39 MPa. Most or all adhesive remained on the tooth after bracket debonding. There were no statistically significant differences in SBS or ARI between the first and second debonding sequences, between the groups, or among the subgroups. Conclusion: With regard to SBS and ARI, SEPs perform as well as CPs for repeated bracket bonding.