Aknin P C, Nanda R S, Duncanson M G, Currier G F, Sinha P K
Department of Orthodontics, College of Dentistry, University of Oklahoma, USA.
Am J Orthod Dentofacial Orthop. 1996 Jan;109(1):22-7.
This study evaluated the fracture strengths of eight new vintage ceramic brackets with application of torsional forces. Palatal root torque was applied at the distal side of right maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x 0.027-inch rounded edge stainless steel arch wire. A specially designed apparatus that attached to an Instron machine was used to test the ceramic brackets. The amount of torque, degrees of torsion at failure, and fracture locations were measured. The monocrystalline bracket did not break when the torquing test was applied; the portion of the wire outside the slot of the bracket twisted on itself. The mean torquing forces at failure ranged from 5755.2 gm-mm to 9316.5 gm-mm and could be separated into three statistically different groups. The mean torsional rotation at fracture ranged from 32.7 degrees to 68.1 degrees for the polycrystalline brackets. The results suggested that all the brackets studied were sufficiently strong to withstand the commonly accepted magnitudes of arch wire torquing forces. The present investigation showed higher angulation values for all the brackets than those reported by Holt who used the same apparatus with older style brackets.
本研究评估了八种新型复古陶瓷托槽在施加扭转力时的断裂强度。通过一根0.0215×0.027英寸的圆角不锈钢弓丝，在右侧上颌中切牙托槽0.022英寸的槽沟远中侧施加腭根转矩。使用一种专门设计的、连接到英斯特朗材料试验机上的装置来测试陶瓷托槽。测量了转矩量、断裂时的扭转度数以及断裂位置。在进行扭转测试时，单晶托槽没有断裂；托槽槽沟外的弓丝部分自身发生了扭转。断裂时的平均扭转力范围为5755.2克·毫米至9316.5克·毫米，可分为三个统计学上不同的组。多晶托槽断裂时的平均扭转角度范围为32.7度至68.1度。结果表明，所研究的所有托槽都足够坚固，能够承受公认的弓丝扭转力大小。本研究显示，所有托槽的角度值均高于Holt使用相同装置对老式托槽所报告的值。
