• Suchon Vatarugegrid D.D.S., Grad. Dip. in Clin. Sc. (Prosthodontics), M.Sc. (Orthodontics)
• Smorntree Viteporn D.D.S. (Hons), M.Sc. (Orthodontics), Cert. in C.F.A (Craniofacial Anomaly), Diplomate, Thai Board of Orthodontics

Objective The purpose of this study was to compare the shear-peel bond strength of metal bracket
to the prepared porcelain surface with two different surface preparations; silane and 1.23% acidulated
phosphate fluoride (APF) gel.

Materials and methods The samples were comprised of 60 porcelain disks (diameter 10 mm, thickness
4 mm). All were unglazed with green stones and then were randomly assigned into 2 groups
(30 specimens each). Group 1 (control), the porcelain surface was prepared with silane. Group 2,
the porcelain surface was etched with 1.23% APF gel for 10 minutes. A central incisor metal bracket
was bonded to the prepared porcelain surface with light-cured adhesive resin and stored in distilled
water at 37 ÌC for 24 hours. The shear-peel bond strength was measured by the Instron Universal
Testing Machine with 250 Newton (N) load cell at 0.5 mm/min crosshead speed. Difference between
the shear-peel bond strength of the two surface preparation procedures was analyzed with independent
sample T-test at p = 0.05. Survival probability of bracket was also analyzed by Weibull analysis.

Results No significant difference was found between the shear-peel bond strength of the APF gel
group (9.42 ± 1.93 megapascals, MPa) and that of the silane group (9.68 ± 1.91 MPa) (p = 0.604).

Conclusion The 1.23% APF gel can probably be an alternative of surface preparation when bonding
metal bracket to porcelain surface after unglazing with a green stone bur.

(CU Dent J. 2010;33:109-18)