Sumi Mayumi, Koga Yoshiyuki, Tominaga Jun-Ya, Hamanaka Ryo, Ozaki Hiroya, Chiang Pao-Chang, Yoshida Noriaki
Postgraduate student, Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Associate professor, Department of Orthodontics, Nagasaki University Hospital, Nagasaki, Japan.
Am J Orthod Dentofacial Orthop. 2016 Dec;150(6):968-978. doi: 10.1016/j.ajodo.2016.05.007.
Most closing loops designed for producing higher moment-to-force (M/F) ratios require complex wire bending and are likely to cause hygiene problems and discomfort because of their complicated configurations. We aimed to develop a simple loop design that can produce optimal force and M/F ratio.
A loop design that can generate a high M/F ratio and the ideal force level was investigated by varying the portion and length of the cross-sectional reduction of a teardrop loop and the loop position. The forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method.
An M/F ratio of 9.3 (high enough to achieve controlled movement of the anterior teeth) and an optimal force level of approximately 250 g of force can be generated by activation of a 10-mm-high teardrop loop whose cross-section of 0.019 × 0.025 or 0.021 × 0.025 in was reduced in thickness by 50% for a distance of 3 mm from the apex, located between a quarter and a third of the interbracket distance from the canine bracket.
The simple loop design that we developed delivers an optimal force and an M/F ratio for the retraction of anterior teeth, and is applicable in a 0.022-in slot system.
大多数用于产生更高力矩与力（M/F）比的闭合曲需要复杂的弯制钢丝，并且由于其复杂的结构可能会导致卫生问题和不适。我们旨在开发一种能够产生最佳力和M/F比的简单曲设计。
通过改变泪滴形曲横截面减小的部分和长度以及曲的位置，研究一种能够产生高M/F比和理想力水平的曲设计。使用基于切线刚度法的结构分析来计算作用于闭合曲上的力和力矩。
激活一个10毫米高的泪滴形曲，其0.019×0.025或0.021×0.025英寸的横截面在距顶点3毫米的距离内厚度减小50%，位于距尖牙托槽间距离的四分之一到三分之一之间，可产生9.3的M/F比（足以实现前牙的可控移动）和约250克力的最佳力水平。
我们开发的这种简单曲设计为前牙后移提供了最佳力和M/F比，并且适用于0.022英寸的槽沟系统。
