Graduate student, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, São Paulo, Brazil.
Professor, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, São Paulo, Brazil.
J Prosthet Dent. 2018 May;119(5):791-796. doi: 10.1016/j.prosdent.2017.07.016. Epub 2017 Sep 28.
Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture.
The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture.
Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone.
In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone.
A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the prosthesis and could minimize the incidence of fracture.
研究表明，对于无牙颌的老年患者，单种植体固位下颌覆盖义齿具有有效性。然而，由于单种植体的壳体部分周围的应力浓度较高，与 2 种植体固位下颌覆盖义齿相比，这种义齿在前部区域更容易断裂。
本有限元分析研究的目的是评估钴铬框架增强的单种植体固位下颌覆盖义齿的应力分布，以尽量减少基托折断的发生率。
在 SolidWorks 2013 软件中设计了两种由单个种植体和牙种植体附着体支撑的下颌覆盖义齿的三维有限元模型。模型之间的唯一区别是在犬齿之间的义齿基托是否存在钴铬框架。随后，将模型导入数学分析软件 ANSYS Workbench v15.0。生成网格，单元尺寸为 0.7mm，并在进行力学模拟之前进行收敛分析。所有材料均被视为均质、各向同性和线弹性的。在 30 度角下，在下颌中切牙的切缘施加 100N 的载荷。计算覆盖义齿的最大主应力、附着体和种植体的 von Mises 应力以及皮质骨和松质骨的最小主应力。
在两种模型中，覆盖义齿的最大应力都集中在种植体周围的前牙凹面区域。然而，与没有框架的覆盖义齿相比，框架的存在使应力降低了近 62%（分别为 8.7MPa 和 22.8MPa）。两种模型在附着体、种植体和骨中的应力值都相似。
单种植体固位下颌覆盖义齿的金属框架加固通过义齿的前区集中较少的应力，从而最大限度地减少断裂的发生。
