Abstract
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 Co, Korea), Non-etched Foil-Mesh base(Dentaurum, 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 $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;90^{\circ}$ 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$(_{60}PBS)$ was in $29\%$ level of shear bond strength and $52\%$ level of tensile bond strength. In Chessboard base group, $_{60}PBS$ was in $34\%$ level of shear bond strength and $61\%$ level of tensile bond strength. In Non-etched Foil-Mesh base group, $_{60}PBS$ 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, $75^{\circ}\;and\;90^{\circ}$ per unit area between Micro-Loc and Chessboard base groups.
본 연구는 교정용 금속 브라켓에 다양한 방향에서의 복합적인 응력을 가하여 힘의 방향과 적용점에 따른 교정용 브라켓의 결합강도를 비교하고, 브라켓의 유지력을 평가하는데 기준이 되는 최소결합강도의 특성에 대해 알아보고자 시행되었다. 일정 한 표면특성을 갖는 금속봉에 Micro-Loc base, Chessboard base, Non-etched Foil-Mesh base 등 서로 다른 기저 면 형태를 가지는 3가지 종류의 금속 브라켓을 부착시키고, $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;90^{\circ}$의 Peel 결합강도$(_0PBS, \;_{15}PBS,\;_{30}PBS,\;_{45}PBS,\;_{60}PBS,\;_{75}PBS,\;_{90}PBS)$ 및 전단결합강도(SBS)와 인장결합강도(TBS)에 대한 브라켓의 결합강도를 측정하고, 각 브라켓의 기저면 면적을 고려하여 단위면적당 결합강도를 산출하여 비교한 결과 다음과 같은 결론을 얻었다. 1. Micro-Loc base와 Chessboard base 및 Non-etched Foil-Mesh base 브라켓 모두에서 전단결합강도(SBS)가 가장 컸다(P<0.01). 2. Peel 응력의 방향 변화에 따른 peel 결합강도(PBS)의 변화양상은 Micro-Loc base와 Chessboard base, Non-etched Foil-Mesh base 브라켓 모두에서 유사하였으며 (p>0.05), peel 응력의 적용 각이 증가할수록 peel 결합강도(PBS)는 감소하였고 $60^{\circ}$에서 최저값을 보였다(p<0.05). 3. Micro-Loc base에서 최저 peel 결합강도$(_{60}PBS)$는 전단결합강도(SBS)의 $29\%$ 수준이었으며, 인장결합강토(TBS)에 대해서는 $52\%$ 수준이었고, Chessboard base에서 최저 Peel bond strength$(_{60}PBS)$는 전단결합강도(SBS)의 $34\%$ 수준이었으며, 인장결합강도(TBS)에 대해서는 $61\%$ 수준이었으며, Non-etched Foil-Mesh base에서 최저 Peel 결합 강도$(_{60}PBS)$는 전단결합강도(SBS)의 $34\%$ 수준이었으며, 인장결합강도(TBS)에 대해서는 $55\%$ 수준이었다. 4. 단위 면적 당 결합강도에 있어서 전단결합강도(SBS)와 인장결합강도(TBS) 및 $75^{\circ}\;와\;90^{\circ}$ peel 결합강도는 Micro-Loc base와 Chessboard base에서 차이 가 없었으며 Non-etched Foil-Mesh base에서 가장 작았고(p<0.05), $0^{\circ},\;15^{\circ},\;30^{\circ},\;60^{\circ}$ peel응력을 적용한 결과 Chessboard base에서 가장 큰 Peel결합강도를, Non-etched Foil-Mesh base에서 가장 작은 결합강도를 보였다(p<0.05).
