The purpose of this study was to investigate the effect of various surface treatment methods on the shear bondstrength of orthodontic brackets in vitro.
Ninety six specimens, 6 mm in diameter and 5 mm in height, were made with composite resin (FiltekTM Z350XT, 3M ESPE, USA) and treated with an aging procedure. After aging, the specimens were randomly separatedin six groups: (1) control with no surface treatment, (2) 37% phosphoric acid gel, (3) 4% hydrofluoric acid gel,(4) sodium bicarbonate particle abrasion, (5) diamond bur, and (6) 1 W carbon dioxide laser for 5s. The metalbrackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT, 3M Unitek,USA). Shear bond strength values were evaluated with a universal testing machine (R&B Inc., Korea).
Analysis of variance showed a significant difference between the groups. Group 5 had the highest mean shearbond strength (11.9 MPa), followed by group 6 (11.1 MPa). Among the experimental groups, group 2 resultedin the weakest mean shear bond strength (5.22 MPa).
The results of this study suggest that the repair shear bond strength of the aged composite resin was acceptableby surface treatment with a carbon dioxide laser.