Department of Prosthodontics, Faculty of Dentistry, University of Selcuk, 42079 Kampus Konya, Turkey.
Clin Oral Investig. 2012 Aug;16(4):1105-10. doi: 10.1007/s00784-011-0606-z. Epub 2011 Aug 16.
This study investigated the influence of the elastic modulus of supporting dies on the fracture strengths of all-ceramic materials used in dental crowns. Four different types of supporting die materials (dentin, epoxy resin, brass, and stainless steel) (24 per group) were prepared using a milling machine to simulate a mandibular molar all-ceramic core preparation. A total number of 96 zirconia cores were fabricated using a CAD/CAM system. The specimens were divided into two groups. In the first group, cores were cemented to substructures using a dual-cure resin cement. In the second group, cores were not cemented to the supporting dies. The specimens were loaded using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. Data were statistically analyzed using two-way analysis of variance and Tukey HSD tests (α = 0.05). The geometric models of cores and supporting die materials were developed using finite element method to obtain the stress distribution of the forces. Cemented groups showed statistically higher fracture strength values than non-cemented groups. While ceramic cores on stainless steel dies showed the highest fracture strength values, ceramic cores on dentin dies showed the lowest fracture strength values among the groups. The elastic modulus of the supporting die structure is a significant factor in determining the fracture resistance of all-ceramic crowns. Using supporting die structures that have a low elastic modulus may be suitable for fracture strength tests, in order to accurately reflect clinical conditions.
本研究探讨了支撑模具的弹性模量对用于牙冠的全瓷材料断裂强度的影响。使用铣床制备了四种不同类型的支撑模具材料（牙本质、环氧树脂、黄铜和不锈钢）（每组 24 个），以模拟下颌磨牙全瓷核预备。使用 CAD/CAM 系统共制作了 96 个氧化锆核。将样本分为两组。在第一组中，使用双固化树脂水泥将核粘接到子结构上。在第二组中，核未粘接到支撑模具上。使用万能试验机以 0.5mm/min 的十字头速度加载样本，直到发生断裂。使用双向方差分析和 Tukey HSD 检验（α=0.05）对数据进行统计分析。使用有限元方法开发了核和支撑模具材料的几何模型，以获得力的应力分布。粘固组的断裂强度值明显高于非粘固组。虽然不锈钢模具上的陶瓷核显示出最高的断裂强度值，但在各组中，牙本质模具上的陶瓷核显示出最低的断裂强度值。支撑模具结构的弹性模量是决定全瓷冠抗断裂能力的重要因素。使用具有低弹性模量的支撑模具结构可能适合进行断裂强度测试，以准确反映临床情况。
