Shear Bond Strength of Metal Brackets to Zirconia Following Different Surface Treatments using a Universal Adhesive

Abstract

Introduction: As there is increase in demand of orthodontic treatment by adult patients, bonding of orthodontic brackets to dental restoration surfaces is now a common necessity because most adult patients have composite resin, amalgam, gold, acrylic resin or ceramic restorations. Orthodontic bracket bonding to teeth restored with zirconia crowns is a challenge in orthodontics. Aim: This study aimed to assess the Shear Bond Strength (SBS) of metal brackets bonded to zirconia with universal adhesive following different surface treatments. Materials and Methods: In this in-vitro study, 30 zirconia blocks (1×1×1 cm) were divided into three groups of 10. One surface of each block was subjected to one of the following three surface treatments: no surface treatment (control group), sandblasting with 50 µM aluminium oxide particles and acid etching with 37% orthophosphoric acid. Metal orthodontic brackets (Dentaurum) were bonded to zirconia blocks using Scotchbond Universal Adhesive (3M) and Transbond XT composite. The SBS was measured at a crosshead speed of 2 mm/minute using a universal testing machine. The fractured surfaces were inspected under a stereomicroscope, and the Adhesive remnant index (ARI) score and the mode of failure were determined. Data were analysed using SPSS 16 via ANOVA and the Kruskal-Wallis test (p<0.05). Results: The SBS values were 12.85±7.16, 19.25±9.07 and 9.89±9.28 MPa in the control, sandblasting and acid etching groups, respectively. The mode of failure was mixed in all groups. No significant difference was noted among the three groups in SBS (p=0.06) or the ARI scores (p=0.19). Conclusion: This study showed that sandblasting or acid etching of zirconia blocks with orthophosphoric acid had no significant effect on SBS of zirconia to metal brackets.

Keywords

• adhesive remnant index
• dental bonding
• orthodontic brackets