Priming and Bonding Metal, Ceramic and Polycarbonate Brackets

Objectives: To investigate the effect of primers on the bonding characteristics of metal, ceramic and polycarbonate brackets to enamel.
Methods: Stainless steel, ceramic zirconia-alumina and polycarbonate brackets were bonded to enamel using bracket material specific/universal primers with orthodontic adhesive (Transbond™XT). The primers in each group (n=10) were silane based (RelyX™ Ceramic Primer) and universal primer (Monobond Plus) for ceramic and metal brackets, and adhesive resin (Adper™ Scotchbond™ Multi-Purpose Adhesive) and composite primer (GC Composite Primer) for polycarbonate brackets. A control group with no primer was used with all bracket types. The primer was applied to bracket base and the bracket was bonded on etched enamel. The specimens were stored in distilled water in 37°C for 7 days and debonded with static loading. Debonding forces were recorded and analysed with ANOVA. Adhesive remnant index (ARI) was determined.
Results: The debonding forces are given in Table 1. The bond strength of brackets without primers was 101.1N (±35.4) for metal, 289.5N (±46.9) for ceramic and 144.9N (±29.1) for polycarbonate brackets, all the values differed significantly (p<0.05). There were no differences between different primers and control group with metal or polycarbonate brackets. The bond strength of ceramic brackets used with silane was 349.6N (±66.1), which was significantly higher compared to the control group and the universal primer group (p<0.05).
ARI scores were mostly 2-3 indicating that all or above 50% of the adhesive was left on the enamel after debonding, except when silane was used with ceramic brackets, where the ARI score was mostly 0-1, indicating that all or above 50% of the adhesive was left on the bracket.
Conclusions: Bonding values were higher for ceramic brackets than for metal or polycarbonate brackets. Primers had only minor effect on the bonding values, except for silane with ceramic brackets, which significantly improved bonding.