Department of Prosthetic Dentistry, Medical University, Lodz, Poland.
J Prosthet Dent. 2011 Feb;105(2):115-26. doi: 10.1016/S0022-3913(11)60011-5.
Previous studies on the strength of teeth restored with posts have not resolved the controversy as to which post systems provide the greatest strength and longevity.
The purpose of this study was to compare the strength of teeth restored using cast posts with those restored using glass fiber-reinforced composite resin posts and to evaluate the bond strength of the posts to dentin.
The investigation was conducted by using finite element analysis, combined with the application of contact elements. Three-dimensional (3-D) models of the maxillary central incisors were generated: IT, an intact tooth; CC, a tooth with a ceramic crown; FP, a tooth restored with an FRC (glass fiber-reinforced composite resin) post; CPAu, a tooth restored with a gold alloy cast post; and CPNi, a tooth restored with an NiCr (nickel chromium alloy) cast post. Each model was subjected to vertical and oblique loads with a force of 100 N. To evaluate the strength of the restored tooth, ceramics, and composite resin, the modified von Mises failure criterion was used, the Tsai-Wu criterion for FRC, and the von Mises criterion for gold and NiCr alloy. The equivalent stresses found in the tested models were compared with the tensile strength of the respective materials. Contact stresses in the luting cement-dentin interface were calculated.
The maximum mvM (modified von Mises failure criterion) stresses in the dentin of the teeth restored with FRC posts were reduced by 21%, and in those restored with cast NiCr posts, stresses were reduced by 25% when compared to the stresses in the intact tooth. The equivalent stresses in metal posts were several times higher than in FRC posts, but did not exceed the tensile strength of the materials. The highest mvM stress in the luting resin cement around the FRC post was 55% higher than in the luting resin cement around the metal post, under an oblique load. In the ceramic crown, which covered the composite resin post and core, the highest mvM stress was 30.7 MPa, whereas with the metal post and core, it was 23 MPa.
Cast metal posts resulted in lower stresses in the dentin of the restored teeth than did FRC posts. Irrespective of the material, the equivalent stresses in the posts did not exceed their tensile strength. Lower stresses were present in the luting cement and the cement-dentin interface around cast posts than around FRC posts. In the ceramic crown supported by a metal post and core, the stresses were lower than those observed in the crown supported by a composite resin core foundation.
之前关于使用桩核修复的牙齿强度的研究尚未解决哪种桩核系统提供最大强度和最长寿命的争议。
本研究的目的是比较铸造桩核修复的牙齿与玻璃纤维增强复合树脂桩核修复的牙齿的强度，并评估桩核与牙本质的粘结强度。
采用有限元分析结合接触元的方法进行研究。生成上颌中切牙的三维（3-D）模型：IT，完整的牙齿；CC，带陶瓷冠的牙齿；FP，用 FRC（玻璃纤维增强复合树脂）桩修复的牙齿；CPAu，用金合金铸造桩修复的牙齿；CPNi，用 NiCr（镍铬合金）铸造桩修复的牙齿。每个模型都受到 100N 的垂直和倾斜载荷。为了评估修复牙、陶瓷和复合树脂的强度，使用修正的 von Mises 失效准则、FRC 的 Tsai-Wu 准则以及金和 NiCr 合金的 von Mises 准则。比较测试模型中的等效应力与各自材料的拉伸强度。计算粘结水泥-牙本质界面处的接触应力。
与完整牙齿相比，用 FRC 桩修复的牙齿的牙本质中最大的 mvM（修正的 von Mises 失效准则）应力降低了 21%，用 NiCr 铸造桩修复的牙齿的应力降低了 25%。金属桩中的等效应力比 FRC 桩高几倍，但未超过材料的拉伸强度。在倾斜载荷下，围绕 FRC 桩的粘结树脂水泥中的最大 mvM 应力比围绕金属桩的粘结树脂水泥高 55%。在覆盖复合树脂桩核的陶瓷冠中，最大的 mvM 应力为 30.7MPa，而用金属桩核时为 23MPa。
铸造金属桩核修复的牙齿的牙本质中的应力低于 FRC 桩核修复的牙齿。无论材料如何，桩核中的等效应力均未超过其拉伸强度。在铸造桩周围的粘结水泥和水泥-牙本质界面处存在较低的应力，而在 FRC 桩周围则存在较高的应力。在由金属桩核支撑的陶瓷冠中，应力低于由复合树脂核基础支撑的冠。
