In vitro evaluation of shear bond strength of orthodontic metal brackets to aged composite using a self-adhesive composite: Effect of surface conditioning and different bonding agents

Objectives > Bracket bonding to composite surfaces is increasing. This study sought to assess the effect of different adhesives (acid etchant + Transbond XT (TM), acid etchant + Vertise Flow (TM), Vertise Flow (TM)) with different surface treatments (no preparation, bur, sandblasting, Er:YAG laser) on shear bond strength (SBS) of metal brackets to aged composite. Materials and methods > In this in vitro, experimental study, Filtek (TM) Z250 composite discs were fabricated (10 x 4 mm). After thermocycling (10,000 cycles between 5-55 degrees C), the samples were randomly divided into three groups (n = 48) based on the type of adhesive namely acid etchant + Transbond XT (TM), Vertise Flow (TM), and acid etchant + Vertise Flow (TM). Samples in each group were randomly divided into four subgroups (n = 12) based on the surface treatment including notreatment, diamond bur, sandblasting and Er:YAG laser. Samples in each group were randomly divided into three subgroups (n = 12) based on the type of adhesive namely acid etchant + Transbond XT (TM), Vertise Flow (TM), and acid etchant + Vertise Flow (TM). After bracket bonding to composite discs, the samples underwent thermocycling (5000 cycles between 5-55 degrees C), and their SBS was measured in a universal testing machine. The samples were then inspected under a stereomicroscope at x10 magnification to determine their mode of failure and adhesive remnant index (ARI). Results > No significant difference was noted in SBS between adhesives in no-preparation and laser groups (P > 0.05). In all adhesive groups, sandblast had highest SBS, but it was not significantly different in Vertise Flow (TM) groups, with and without etching. The SBS provided by acid etchant + Transbond XT (TM) was significantly higher than that of the other two adhesives (P < 0.05). The SBS of sandblasted samples was significantly higher compared with other surface treatments in all adhesive subgroups (P < 0.05). Conclusion > Bracket bonding to aged composite using Vertise Flow (TM) with or without surface treatment can serve as an alternative to the conventional orthodontic adhesives.