Memari Yeghaneh, Fattahi Parisa, Fattahi Amir, Eskandarion Solmaz, Rakhshan Vahid
Removable Prosthesis Department, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Department of Restorative Dentistry, School of Dentistry, Islamic Azad University, Tehran, Iran.
Dent Res J (Isfahan). 2020 Jan 21;17(1):25-33. eCollection 2020 Jan-Feb.
Optimal stress distribution around implants plays an important role in the success of mandibular overdentures. This study sought to assess the pattern of stress distribution around short (6 mm) and long (10 mm) implants in mandibular two implant-supported overdentures using finite element analysis (FEA).
In this descriptive and experimental study two implant-supported overdenture models with bar and clip attachment system on an edentulous mandible were used. Two vertical implants were connected by a bar. The implant length was 6 mm (short implant) in the first and 10 mm (long implant) in the second model. Vertical loads (35, 65, and 100 N) were applied bilaterally to the second molar area. In another analysis, vertical loads of 43.3 N and 21.6 N were applied to working and nonworking sides, respectively, at the second molar area. Furthermore, the lateral force (17.5 N) was applied to the canine area of overdenture. The stress distribution pattern around implants was analyzed using FEA.
The maximum von Mises stress was 57, 106, and 164 MPa around short implants and 64, 118, and 172 MPa around long implants following the application of 35, 65, and 100 N bilateral forces, respectively. Application of bilateral loads created 87 and 65 MPa stress around working and nonworking short implants, respectively; while these values were reported to be 92 and 76 MPa for long implants at the working and nonworking sides, respectively. Increasing the vertical loads increased the level of stress distributed around the implants; however, no considerable differences were noted between long and short implants for similar forces. Following unequal load application, the stress in the working side bone was more than that in the nonworking side, but no major differences were noted in similar areas around long and short implants. Following lateral load application, the stress distributed in the peri-implant bone at the force side was more than that in the opposite side. In similar areas, no notable differences were observed between long and short implants regarding the maximum stress values.
Using implants with different lengths in mandibular overdenture caused no major changes in stress distribution in peri-implant bone; short implants were somehow comparable to long implants.
种植体周围的最佳应力分布在下颌覆盖义齿的成功中起着重要作用。本研究旨在使用有限元分析（FEA）评估下颌双种植体支持覆盖义齿中短（6mm）种植体和长（10mm）种植体周围的应力分布模式。
在这项描述性和实验性研究中，使用了两个在无牙下颌上带有杆和卡环附着系统的种植体支持覆盖义齿模型。两个垂直种植体通过一根杆连接。第一个模型中的种植体长度为6mm（短种植体），第二个模型中的种植体长度为10mm（长种植体）。双侧在第二磨牙区域施加垂直载荷（35、65和100N）。在另一项分析中，在第二磨牙区域分别向工作侧和非工作侧施加43.3N和21.6N的垂直载荷。此外，向覆盖义齿的尖牙区域施加侧向力（17.5N）。使用FEA分析种植体周围的应力分布模式。
在分别施加35、65和100N双侧力后，短种植体周围的最大冯·米塞斯应力分别为57、106和164MPa，长种植体周围的最大冯·米塞斯应力分别为64、118和172MPa。施加双侧载荷时，工作侧和非工作侧短种植体周围产生的应力分别为87和65MPa；而长种植体在工作侧和非工作侧的这些值分别报告为92和76MPa。增加垂直载荷会增加种植体周围分布的应力水平；然而，对于相似的力，长种植体和短种植体之间未观察到显著差异。在施加不等载荷后，工作侧骨中的应力大于非工作侧，但在长种植体和短种植体周围的相似区域未观察到重大差异。在施加侧向载荷后，力侧种植体周围骨中分布的应力大于对侧。在相似区域，长种植体和短种植体在最大应力值方面未观察到显著差异。
在下颌覆盖义齿中使用不同长度的种植体不会导致种植体周围骨中应力分布的重大变化；短种植体在某种程度上与长种植体相当。
