FINITE-ELEMENT ANALYSIS OF 3-UNIT AND 4-UNIT BRIDGES
FINITE-ELEMENT ANALYSIS OF 3-UNIT AND 4-UNIT BRIDGES
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DOI：
10.1111/j.1365-2842.1989.tb01384.x
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发表时间：
1989-11-01
影响因子：
2.9
通讯作者：
MEROUEH, KA
中科院分区：
文献类型：
--
作者：
FARAH, JW;CRAIG, RG;MEROUEH, KA
使用下颌象限的二维有限元模型来检验三单元桥和四单元桥的放置对主应力大小的影响。感兴趣的区域从第一个前磨牙到第二个磨牙。加载条件为：(I)垂直分布，(Ii)垂直30°，集中。计算和比较的主应力是：(I)第一磨牙被移除，剩余的骨质被皮质壳包围；(Ii)与(I)相同，但第二前磨牙和第一磨牙被移除；(Iii)横跨第二前磨牙和第二磨牙的三单元桥；以及(Iv)横跨第一前磨牙和第二磨牙的四单元桥。每颗牙齿由牙周韧带、皮质骨和松质骨支撑，每一根牙都分配了适当的物理常数。拔除第一磨牙会导致应力的显著变化，特别是当皮质壳被松质骨取代时。由于松质骨的模数较低，承载能力较低，松质骨内的应力较小，且更加均匀。一般而言，桥的增加导致较低且分布较好的σ最小应力。桥还导致基牙远端较高的拉应力，这在理论上可能会导致骨沉积。在三单元和四单元桥梁之间没有观察到显著的震级差异。从应力的角度来看，桥基周围的应力分布更加均匀，基牙远侧的拉应力增大。这些发现支持放置固定桥以维持无牙区的骨。
A two‐dimensional finite element model of a mandibular quadrant was used to examine differences in magnitude of the principal stresses from the placement of three‐ and four‐unit bridges. The area of interest spanned the first premolar to the second molar. Loading conditions were (i) vertical and distributed and (ii) 30° to the vertical and concentrated. The principal stresses were calculated and compared for: (i) the first molar removed with the remaining bone either cancellous or cancellous surrounded by a cortical shell; (ii) as in (i) but with the second premolar and first molar removed; (iii) a three‐unit bridge spanning the second premolar to the second molar; and (iv) a four‐unit bridge spanning the first premolar to the second molar. Each tooth was supported by periodontal ligaments, cortical and cancellous bone with each assigned the appropriate physical constants. Removal of the first molar resulted in considerable variation of the stresses especially when the cortical shell was replaced by cancellous bone. Because of the lower modulus of cancellous bone and its lower load‐bearing capabilities the stresses were three to ten times lower and more uniform within the cancellous bone. Generally, the addition of a bridge resulted in lower and better distributed σminstresses. The bridge also resulted in higher tensile stresses distal to the abutment teeth which theoretically could result in bone deposition. No significant differences in magnitude were observed between the three‐ and four‐unit bridge. From a stress standpoint the bridges resulted in more uniform stress distribution around the abutments and an increase in the tensile stresses distal to the abutments. Such findings support the placement of a fixed bridge to maintain bone in an edentulous area.