Nishihara K, Nakagiri S
Department of Oral Surgery, Faculty of Medicine, University of Tokyo, Japan.
Biomed Mater Eng. 1994;4(3):141-9.
Artificial roots must carry multiple forces during mastication. Stress distribution around a root depends upon the shape, material, and function of the root. Therefore, for biomechanical studies on artificial roots, triad research on the material, shape, and functional effect upon surrounding tissue is essential. For dental implants, there are two different functional systems against the masticatory force, i.e., gomphosis and ankylosis on osseointegration. Stress analyses of functioning new type (gomphosis) artificial roots were carried out in mandibular and maxilla models to study the triad effect using finite element analysis. The authors have already reported histological and biomechanical studies on the shape and functional effect. To observe the material effect biomechanically, artificial roots made of sintered hydroxyapatite and zirconium oxide were analyzed in the models. Thereafter, animal experiments using dogs were carried out to observe bone formation around artificial roots made of hydroxyapatite and zirconium oxide in the mandible and maxilla. The following results were obtained: The patterns of stress distribution around artificial roots of two different materials were not too different, and were exclusively dependent upon the root shape and structure of the jawbone. Around the artificial roots, bone formation coincided with a moderate stress distributing zone and principal stress trajectories. Through these experiments, the following conclusions were obtained: (a) Osteogenesis around artificial roots coincides with the stress distribution patterns. (b) Stress distribution patterns are dependent very little upon material properties but upon both the artificial root shape and the structure of the jawbone. (c) Optimization of the artificial root shape can be obtained by FEA in the models.
人工牙根在咀嚼过程中必须承受多种力量。牙根周围的应力分布取决于牙根的形状、材料和功能。因此，对于人工牙根的生物力学研究，对材料、形状以及对周围组织的功能影响进行三方面的研究至关重要。对于牙种植体，存在两种抵抗咀嚼力的不同功能系统，即骨结合时的牙周膜纤维连接和骨性粘连。为了利用有限元分析研究三方面的影响，在下颌骨和上颌骨模型中对新型（牙周膜纤维连接型）功能人工牙根进行了应力分析。作者已经报道了关于形状和功能影响的组织学和生物力学研究。为了从生物力学角度观察材料的影响，在模型中分析了由烧结羟基磷灰石和氧化锆制成的人工牙根。此后，进行了使用犬的动物实验，以观察下颌骨和上颌骨中由羟基磷灰石和氧化锆制成的人工牙根周围的骨形成情况。得到了以下结果：两种不同材料的人工牙根周围的应力分布模式差异不大，且完全取决于牙根形状和颌骨结构。在人工牙根周围，骨形成与适度应力分布区和主应力轨迹一致。通过这些实验，得出了以下结论：(a)人工牙根周围的骨生成与应力分布模式一致。(b)应力分布模式几乎不取决于材料特性，而是取决于人工牙根形状和颌骨结构。(c)通过模型中的有限元分析可以实现人工牙根形状的优化。
