Effect of Four Methods of Surface Treatment on Shear Bond Strength of Orthodontic Brackets to Zirconium
Objectives: Providing reliable attachment between bracket base and zirconia surface is a prerequisite for exertion of orthodontic force. The purpose of the present study was to eval- uate the effect of four zirconium surface treatment methods on shear bond strength (SBS) of orthodontic brackets.
Materials and Methods: One block of zirconium was trimmed into four zirconium sur- faces, which served as our four study groups and each had 18 metal brackets bonded to them. Once the glazed layer was removed, the first group was etched with 9.6% hydrofluoric acid (HF), and the other three groups were prepared by means of sandblasting and 1 W, and 2 W Er: YAG laser, respectively. After application of silane, central incisor brackets were bonded to the zirconium surfaces. The SBS values were measured by a Dartec testing ma- chine with a crosshead speed of 1 mm/min.
Results: The highest SBS was achieved in the sandblasted group (7.81±1.02 MPa) followed in a descending order by 2 W laser group (6.95±0.87 MPa), 1 W laser group (6.87±0.92MPa) and HF acid etched group (5.84±0.78 MPa). The differences between the study groups, were statistically significant except between the laser groups (P < 0.05).
Conclusion: In terms of higher bond strength and safety, sandblasting and Er: YAG laser irradiation with power output of 1 W and 2 W can be considered more appropriate alterna- tives to HF acid etching for zirconium surface treatment prior to bracket bonding.