Department of Prosthetic Dentistry, Medical University of Lodz, Lodz, Poland.
Dent Mater. 2012 Apr;28(4):433-41. doi: 10.1016/j.dental.2011.11.019. Epub 2011 Dec 29.
The aim of the study was to compare the strength of thin-walled molar crowns made of various materials under simulation of mastication.
Five 3D FE models of the first lower molar with the use of contact elements were created: intact tooth; tooth with a zirconia crown; tooth with a porcelain crown; tooth with a gold alloy crown and tooth with a composite crown. The computer simulations of mastication were conducted. For the models, equivalent stresseswere calculated using the modified von Mises failure criterion (mvM). Contact stresses at the adhesive interface between the cement and tooth structure under the crowns were analyzed.
Equivalent stresses in the crowns, did not exceed the tensile strength of their material. The mvM stresses in resin cement under the zirconia crown were 1.3 MPa, and under the composite crown they increased over 6 times. The tensile and shear contact stressesunder the stiff crowns (ceramics and gold alloy), were several times lower than those under the composite one. The maximum mvM stresses in the tooth structure for the zirconia crown were only 2.8 MPa, whereas for the composite crown were 6.4 MPa. The higher elastic modulus the crown was, the lower the equivalent stresses occurred in the composite luting cement and in the tooth structures. Also contact stresses decreased with the increasing stiffness of the crowns.
Under physiological loads, the thin-walled crowns perfectly luted to molars, made of zirconia ceramic, gold alloys and composite resin are resistant to failure. Prosthetic crowns made of stiff materials are less prone to debonding than those made of composite resin. Prosthetic crowns made of a material with a higher elastic modulus than enamel will strengthen the dental structures of molar teeth.
本研究旨在模拟咀嚼过程，比较不同材料制成的薄壁磨牙冠的强度。
使用接触元创建了 5 个具有第一下磨牙的 3D FE 模型：完整的牙齿；氧化锆冠的牙齿；瓷冠的牙齿；金合金冠的牙齿和复合冠的牙齿。进行咀嚼的计算机模拟。对于模型，使用修正的 von Mises 失效准则（mvM）计算等效应力。分析了冠下的粘结剂和牙体结构之间的粘结界面的接触应力。
冠内的等效应力没有超过其材料的拉伸强度。氧化锆冠下树脂水泥中的 mvM 应力为 1.3 MPa，而复合冠下则增加了 6 倍以上。在硬冠（陶瓷和金合金）下的拉伸和剪切接触应力要比在复合冠下低几倍。氧化锆冠下牙齿结构中的最大 mvM 应力仅为 2.8 MPa，而复合冠下为 6.4 MPa。冠的弹性模量越高，复合粘固水泥和牙体结构中的等效应力越低。同时，随着冠的刚度增加，接触应力也会降低。
在生理负荷下，与磨牙完美粘结的薄壁冠，由氧化锆陶瓷、金合金和复合树脂制成，不易失效。由刚性材料制成的修复体比由复合材料制成的修复体更不易脱粘。与牙釉质弹性模量更高的材料制成的修复体将增强磨牙的牙体结构。
