Papers by Author: H.B. Yim

Abstract: Adhesion characteristics of base-coated single crystal brackets for orthodontics were investigated to evaluate the feasibility for the ceramic bracket applications. Sapphire single crystal ingot were machined, abraded and spray-coated with slurries containing 50 wt% of flux and 40µm, 80µm and 150µm of granules. Maximum adhesion to the base surface of the brackets was observed when the size of granule in the slurries was 80µm. It may be due to higher bonding area of adhesive to granule and to base as a result of interlocking structure which has moderate thickness and uniform distribution of granules. The one-way analysis of variance indicated that there were not significant differences in bond strength measurements between the once and twice coating condition in 80µm and 150µm granule groups. But ARI values exhibited large differences between once and twice coating groups and showed different median or ranges. Adhesive remnant of adhesive resin was minimized when the slurry of 80µm granule was coated once. 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 (12.9 MPa) and no adhesive remnant were newly proposed for the orthodontics applications.

Abstract: 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.