Gonda Tomoya, Yasuda Daiisa, Ikebe Kazunori, Maeda Yoshinobu
Int J Oral Maxillofac Implants. 2014 Nov-Dec;29(6):e275-82. doi: 10.11607/jomi.3663.
Although the risks of using a cantilever to treat missing teeth have been described, the mechanisms remain unclear. This study aimed to reveal these mechanisms from a biomechanical perspective. The effects of various implant sites, number of implants, and superstructural connections on stress distribution in the marginal bone were analyzed with three-dimensional finite element models based on mandibular computed tomography data. Forces from the masseter, temporalis, and internal pterygoid were applied as vectors.
Two three-dimensional finite element models were created with the edentulous mandible showing severe and relatively modest residual ridge resorption. Cantilevers of the premolar and molar were simulated in the superstructures in the models. The following conditions were also included as factors in the models to investigate changes: poor bone quality, shortened dental arch, posterior occlusion, lateral occlusion, double force of the masseter, and short implant. Multiple linear regression analysis with a forced-entry method was performed with stress values as the objective variable and the factors as the explanatory variable.
When bone mass was high, stress around the implant caused by differences in implantation sites was reduced. When bone mass was low, the presence of a cantilever was a possible risk factor. The stress around the implant increased significantly if bone quality was poor or if increased force (eg, bruxism) was applied.
The addition of a cantilever to the superstructure increased stress around implants. When large muscle forces were applied to a superstructure with cantilevers or if bone quality was poor, stress around the implants increased.
尽管已描述了使用悬臂梁治疗牙齿缺失的风险，但其机制仍不清楚。本研究旨在从生物力学角度揭示这些机制。基于下颌计算机断层扫描数据，利用三维有限元模型分析了不同种植部位、种植体数量和上部结构连接对边缘骨应力分布的影响。将咬肌、颞肌和翼内肌产生的力作为向量施加。
创建了两个无牙下颌的三维有限元模型，分别显示严重和相对适度的剩余牙槽嵴吸收。在模型的上部结构中模拟了前磨牙和磨牙的悬臂梁。模型中还包括以下条件作为因素来研究变化：骨质差、牙弓缩短、后牙咬合、侧方咬合、咬肌双重力量和种植体短。以应力值为目标变量，以这些因素为解释变量，采用强制进入法进行多元线性回归分析。
当骨量高时，种植部位差异引起的种植体周围应力降低。当骨量低时，存在悬臂梁是一个可能的危险因素。如果骨质差或施加增加的力（如磨牙症），种植体周围的应力会显著增加。
在上部结构中增加悬臂梁会增加种植体周围的应力。当对带有悬臂梁的上部结构施加较大肌肉力量或骨质较差时，种植体周围的应力会增加。
