Mosharraf Ramin, Molaei Paria, Fathi Amirhossein, Isler Sabire
Department of Prosthodontics, Dental Materials Research Center, Dental Research Institute, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
Dental Students' Research Committee, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
Int J Dent. 2021 Nov 12;2021:5977994. doi: 10.1155/2021/5977994. eCollection 2021.
This study was designed to assess the effect of nonrigid connectors (NRCs) and their location in the success of tooth-and-implant-supported fixed prostheses in the maxillary anterior region by finite element analysis (FEA).
Three 3D FEA models were designed, presuming maxillary lateral incisor and canine to be extracted. Implant (replacing canine), abutment, bone (spongious and cortical), central incisor (containing dentin, root cement, gutta-percha, and casting post and core), periodontal ligament, and three three-unit cemented PFM prostheses (a rigid one and two nonrigid) were modeled. The NRC was once in the tooth side and once in the implant side. The prostheses were loaded twice: 250N to the incisal edges (0° to the long axis) and 200 N to the cingula (45° to the long axis). The von-Mises stress and vertical displacement were analyzed.
Under both vertical and oblique loadings, the rigid model presented the highest stress. Under vertical loading, the NRC caused a significant decrease in the applied stress to the prosthesis, bone, implant, and tooth. Locating the NRC in the tooth side decreased the applied stress to the prosthesis and NRC. Under oblique loading, prosthesis and implant tolerated less stress in the presence of an NRC. Placing the NRC in the tooth side resulted in the least stress in all of the components except for porcelain and patrix. Vertical displacement of the tooth apex was approximately equal in all models.
Using an NRC on the tooth side is the most efficient method in reducing the applied stress to prosthesis, implant, tooth, and bone. The amount of intrusion is not dependent on using an NRC or not.
本研究旨在通过有限元分析（FEA）评估非刚性连接体（NRC）及其位置对上颌前部牙齿和种植体支持的固定修复体成功的影响。
设计了三个三维有限元分析模型，假设拔除上颌侧切牙和尖牙。对种植体（替代尖牙）、基台、骨（松质骨和皮质骨）、中切牙（包含牙本质、牙根粘固剂、牙胶和铸造桩核）、牙周膜以及三个三单位粘结式烤瓷熔附金属修复体（一个刚性修复体和两个非刚性修复体）进行建模。NRC一次位于牙齿侧，一次位于种植体侧。修复体加载两次：向切缘施加250N（与长轴成0°），向舌隆突施加200N（与长轴成45°）。分析von-Mises应力和垂直位移。
在垂直和斜向加载下，刚性模型的应力最高。在垂直加载下，NRC使施加于修复体、骨、种植体和牙齿的应力显著降低。将NRC置于牙齿侧可降低施加于修复体和NRC的应力。在斜向加载下，存在NRC时修复体和种植体承受的应力较小。将NRC置于牙齿侧时，除瓷和基体之外的所有部件中的应力最小。所有模型中根尖的垂直位移大致相等。
在牙齿侧使用NRC是降低施加于修复体、种植体、牙齿和骨的应力的最有效方法。侵入量与是否使用NRC无关。
