Lewis G, Manickam S, Smart F M
Department of Mechanical Engineering, University of Memphis, TN 38152, USA.
Biomed Mater Eng. 1996;6(1):33-45.
The finite element analysis method and a two-dimensional idealization were used to conduct a detailed parametric study of the stresses in and displacement of models of bonded edgewise "combination-materials" type of orthodontic brackets when subjected to loading and constraint conditions that are deemed to be the same as those that exist in vivo. A "combination-materials" type bracket is herein defined as one in which different materials are used in fabricating the main body and the archwire slot. The present study was conducted in three parts. In Part 1, 16 model cases were analyzed, involving 4 different combinations of materials (for the main body of the bracket and its archwire slot) and 4 different overall bracket configurations (comprising main body, base and slot). The focus of Part 2 was the model bracket configuration that was, on the basis of Part 1 results, deemed to show the "optimum performance". In this part, the parameter investigated was the value of the modulus of elasticity of the adhesive, Eadh. In Part 3, the concept of an efficiency index of the bonded bracket-archwire system, eta, was introduced and explained. The dependence of eta on stated characteristics of a rectangular archwire, for the "optimum performance" model, was explored. Part 1 results led to the conclusion that the "optimum performance" model has equally angulated buccal and lingual edges and the main body and archwire slot are fabricated from glass fiber-reinforced polycarbonate and stainless steel, respectively. Part 2 results showed that, for the aforementioned "optimum performance" model, the longitudinal displacement of the archwire slot is fairly insensitive to Eadh. Part 3 results showed that eta is intimately related to each of the wire characteristics studied (namely cross-sectional dimensions, "interbracket distance" and modulus of rigidity of the material).
采用有限元分析方法和二维理想化方法，对粘结式边缘“组合材料”型正畸托槽模型在与体内相同的加载和约束条件下的应力和位移进行了详细的参数研究。本文将“组合材料”型托槽定义为在制造主体和弓丝槽时使用不同材料的托槽。本研究分三个部分进行。在第1部分中，分析了16个模型案例，涉及4种不同的材料组合（用于托槽主体及其弓丝槽）和4种不同的整体托槽构型（包括主体、底座和槽）。第2部分的重点是基于第1部分结果被认为显示“最佳性能”的模型托槽构型。在这一部分中，研究的参数是粘合剂的弹性模量Eadh的值。在第3部分中，引入并解释了粘结托槽-弓丝系统效率指数eta的概念。探讨了eta对于“最佳性能”模型的矩形弓丝的规定特性的依赖性。第1部分的结果得出结论，“最佳性能”模型的颊侧和舌侧边缘角度相等，主体和弓丝槽分别由玻璃纤维增强聚碳酸酯和不锈钢制成。第2部分的结果表明，对于上述“最佳性能”模型，弓丝槽的纵向位移对Eadh相当不敏感。第3部分的结果表明，eta与所研究的每个弓丝特性（即横截面尺寸、“托槽间距”和材料的刚性模量）密切相关。
