The purpose of this study was to evaluate the bond strength of orthodontic brackets bonded to metal bar with chemically cured adhesive (Ortho-one, Bisco Co, USA) in various types and directions of force application. Three types of metal bracket with different bracket base configurations; Micro-Loc base(Tomy Co, Japan); Chessboard base(Daesung (Zo, Korea), Non-etched Foil-Mesh base(Dentauru n, Germany); were used in this study. Peel, shear, -tensile bond strengths were measured by universal testing machine and compared each other. The peel force directions applied were 00, 150, 30°, 45°, 60° 75° 90° And then, in consideration of the different surface area of the bracket bases, the bond strength -per unit area were calculated and compared.
The results obtained were summarized as follows
1. The bond strengths according to the types and the directions of the forces were greatest at the shear forces in all three bracket base configuration groups(p<0.01).
2. As the peel force direction grew higher in degree, peel bond strength decreased The patterns of peel bond strength change according to force direction was similar in all three bracket base configurations. The minimum bond strength was 60 degree-peel bond strengths in all three bracket base configurations.
3. In Micro-Loc base group, minimum peel bond strength(soPBS) was in 29% level of shear bond strength and 52% level of tensile bond strength. In Chessboard base group, 6oPBS was in 34% level of shear bond strength and 61% level of tensile bond strength. In Non-etched Foil-Mesh base group, enPBS was in 34% level of shear bond strength and 55% level of tensile bond strength.
4. The bond strengths per unit area were lowest in Non-etched Foil-Mesh base group and highest in Chessboard base group(p<0.05). However, there were no differences in shear bond strength, tensile bond strength, 7sPBS and soPBS per unit area between Micro-Loc and Chessboard base groups.
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