Santos Andrea F V, Tanaka Carina B, Lima Raul G, Espósito Camila O M, Ballester Rafael Y, Braga Roberto R, Meira Josete B C
Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil.
J Endod. 2009 Jan;35(1):117-20. doi: 10.1016/j.joen.2008.09.021. Epub 2008 Nov 8.
Upper premolars restored with endodontic posts present a high incidence of vertical root fracture (VRF). Two hypotheses were tested: (1) the smaller mesiodistal diameter favors stress concentration in the root and (2) the lack of an effective bonding between root and post increases the risk of VRF. Using finite element analysis, maximum principal stress was analyzed in 3-dimensional intact upper second premolar models. From the intact models, new models were built including endodontic posts of different elastic modulus (E = 37 or E = 200 GPa) with circular or oval cross-section, either bonded or nonbonded to circular or oval cross-section root canals. The first hypothesis was partially confirmed because the conditions involving nonbonded, low-modulus posts showed lower tensile stress for oval canals compared to circular canals. Tensile stress peaks for the nonbonded models were approximately three times higher than for the bonded or intact models, therefore confirming the second hypothesis.
用根管桩修复的上颌前磨牙垂直根折（VRF）发生率很高。测试了两种假设：（1）近远中直径较小有利于牙根应力集中；（2）牙根与桩之间缺乏有效的粘结会增加垂直根折的风险。使用有限元分析，在三维完整的上颌第二前磨牙模型中分析最大主应力。从完整模型开始，构建了新模型，包括具有圆形或椭圆形横截面、与圆形或椭圆形横截面根管粘结或不粘结的不同弹性模量（E = 37或E = 200 GPa）的根管桩。第一个假设得到部分证实，因为与圆形根管相比，涉及未粘结、低模量桩的椭圆形根管条件下的拉应力较低。未粘结模型的拉应力峰值比粘结或完整模型高约三倍，因此证实了第二个假设。
