Lan Ting-Hsun, Liu Pao-Hsin, Chou Mitch M C, Lee Huey-Er
Attending Dentist, Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung Taiwan; Assistant Professor, School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Assistant Professor, Department of Biomedical Engineering, I-Shou University, Kaohsiung, Taiwan.
J Prosthet Dent. 2016 Jan;115(1):76-83. doi: 10.1016/j.prosdent.2015.06.021. Epub 2015 Sep 26.
The use of monolithic zirconia crowns in implant prostheses is increasing, especially when the interdental space is insufficient. However, fractures have been reported in clinical practice.
The purpose of this study was to determine the minimal thickness of a complete zirconia crown used for an implant prosthesis in the posterior dental region.
Fifty complete zirconia crowns were produced using a computer-aided design/computer-aided manufacturing technique. In each group, 5 crowns of varying thicknesses (0.4, 0.5, 0.6, 0.7, and 0.8 mm) were subjected to cycles of vertical and 10-degree oblique compressive loading at 5 Hz and 300 N in a servohydraulic testing machine. Five finite element models comprising 5 different occlusal thicknesses (0.4, 0.5, 0.6, 0.7, and 0.8 mm) were simulated at 2 loading angles (0 and 10 degrees) and 3 loading forces (300, 500, and 800 N). Data were statistically analyzed, and fracture patterns were observed with a scanning electron microscope.
Cyclic loading tests revealed that the fracture resistance of the specimens was positively associated with prosthesis thickness (P<.01). Low von Mises stress values were obtained for prostheses with a minimal thickness of 0.7 mm under varying loading directions and forces.
Zirconia prostheses with a minimal thickness of 0.7 mm had a high fracture resistance and the lowest stress values. Therefore, dentists and laboratory technicians should carefully choose the optimum thickness of zirconia prostheses.
整体式氧化锆牙冠在种植修复体中的应用正在增加，尤其是在牙间隙不足时。然而，临床实践中已报道有牙冠折断的情况。
本研究的目的是确定用于后牙区种植修复体的完整氧化锆牙冠的最小厚度。
采用计算机辅助设计/计算机辅助制造技术制作50个完整的氧化锆牙冠。在每组中，5个不同厚度（0.4、0.5、0.6、0.7和0.8毫米）的牙冠在伺服液压试验机中以5赫兹的频率和300牛的力承受垂直和10度斜向压缩加载循环。模拟了5个包含5种不同咬合厚度（0.4、0.5、0.6、0.7和0.8毫米）的有限元模型，加载角度为2种（0度和10度），加载力为3种（300、500和800牛）。对数据进行统计学分析，并用扫描电子显微镜观察折断模式。
循环加载试验表明，试件的抗折性与修复体厚度呈正相关（P<0.01）。在不同加载方向和力的情况下，最小厚度为0.7毫米的修复体获得了较低的冯·米塞斯应力值。
最小厚度为0.7毫米的氧化锆修复体具有较高的抗折性和最低的应力值。因此，牙医和实验室技术人员应谨慎选择氧化锆修复体的最佳厚度。
