In Vitro Bond Strength of Based-Coated Zirconia Brackets for Orthodontics

In Vitro Bond strength of base-coated (Y, Fe)-TZPs (yttria and iron co-doped tetragonal zirconia polycrystals) were investigated to evaluate the feasibility for the ceramic bracket applications. Pre-sintered (Y,Fe)-TZP brackets were machined, abraded and spray-coated with granule slurries containing 10~50 wt% of flux. Better adhesion to the base surface of the brackets was observed by raising the amount of flux in the slurries. It may be because of the fusion and the collapse of the granules as a result of the high amount of flux. The one-way analysis of variance indicated that there were significant differences in bond strength measurements between the experimental groups except 30% and 50% flux content groups. The Weibull distribution revealed that 50% flux content group is the best with a high characteristic strength value. Mean ARI values exhibited large differences and ranged from 1.6 for 50% flux content group to 3.0 for non-coated group. Adhesive remnant of adhesive resin was decreased by increasing the flux up to 50%. Reduction in adhesive remnant is likely due to the higher bonding of adhesive resin to granules. No teeth and bracket damages were found in any teeth de-bonded by shear force. The base-coated brackets with higher strength (11.5 MPa) and no adhesive remnant were newly proposed for the orthodontics applications.