Natali Arturo N, Carniel Emanuele L, Pavan Piero G
Centre of Mechanics of Biological Materials, University of Padova Via F. Marzolo 9, I-3531 Padova, Italy.
Dent Mater. 2008 Apr;24(4):561-9. doi: 10.1016/j.dental.2007.11.024. Epub 2008 Jan 18.
The aim of the paper is to analyze the effects of misfits in multi-implant oral prostheses caused by defects in manufacturing of bar connecting implants. The consequent stress-strain state on peri-implant bone tissue must be carefully considered because of the significant effects induced.
The case of a two-implant prosthesis connected by a titanium cast bar in the pre-molar mandible region is investigated. The complex geometry requires the use of refined finite element model. In consideration of the action induced on the bone tissue, a specific constitutive model that includes inelastic behavior is implemented. The linear misfits considered, estimated with reference to experimental works already present in the literature, induce relevant strains in the peri-implant bone tissue up to a post-elastic phase. Relaxation phenomena are also evaluated. The interaction between the bone and implant is modeled by using contact elements to represent possible detachments at the bone-implant interface.
The response of the bone material is reported with regard to the stress/strain field induced, evaluating the inelastic behavior in terms of plastic and relaxation responses. The effects on the peri-implant bone tissue at the interface are evaluated.
The analysis confirms that the interaction phenomena between the multi-implant oral prostheses and bone induced by the misfit defects of normal intensity induce significant strain in the bone tissue and inelastic phenomena must be taken into account. Local permanent strains of bone tissue and relaxation phenomena represent short-term tissue response for a correct interpretation of the real biomechanical behavior of multiple implant frames.
本文旨在分析杆连接种植体制造缺陷导致的多颗种植体口腔修复体不匹配的影响。由于所产生的显著影响，必须仔细考虑种植体周围骨组织上随之产生的应力应变状态。
研究下颌前磨牙区两颗种植体通过钛铸造杆连接的修复体案例。复杂的几何形状需要使用精细的有限元模型。考虑到对骨组织产生的作用，实施了一种包含非弹性行为的特定本构模型。参考已发表文献中的实验工作估算的线性不匹配，在种植体周围骨组织中会引起直至弹性后阶段的相关应变。还评估了松弛现象。通过使用接触单元来模拟骨与种植体之间的相互作用，以表示骨 - 种植体界面处可能的分离。
报告了骨材料对应力/应变场的响应，从塑性和松弛响应方面评估非弹性行为。评估了对界面处种植体周围骨组织的影响。
分析证实，正常强度的不匹配缺陷所引起的多颗种植体口腔修复体与骨之间的相互作用现象会在骨组织中引起显著应变，必须考虑非弹性现象。骨组织的局部永久应变和松弛现象代表了短期组织响应，有助于正确解释多颗种植体框架的实际生物力学行为。
