De Andrade Guilherme S, Tribst João Paulo M, Orozco Esteban If, Augusto Marina G, Bottino Marco A, Borges Alexandre Ls, Anami Lilian C, Saavedra Guilherme deSFA
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, São José dos Campos, SP, Brazil.
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, São José dos Campos, SP, Brazil,
Am J Dent. 2020 Oct;33(5):227-234.
To evaluate the influence of different post-endodontic techniques on the fatigue survival and biomechanical behavior of crowned restored central incisors.
The crowns of 69 bovine incisors were cut, and the roots were treated endodontically and assigned randomly into three groups (n=23): resin composite buildup (BUP), glass fiber post-retained resin composite buildup (GFP), and cast post-and-core (CPC). They received full crown preparation with 2 mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining specimens were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 x 10⁶ cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level. The three groups tested (BUP, GFP, and CPC) were 3D modeled (Rhinoceros 4.0) and the maximum principal stress (MPa) criteria were used to calculate the results using FEA.
There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X²= 0.015, df=1, P= 0.901, X²=3.171, df=1, P= 0.995). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC. In endodontically treated incisors with a 2-mm ferrule, the post-endodontic treatment had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts.
Although the clinical significance of laboratory studies has some limitations, this study suggests that composite buildups without posts may be an option for restoring endodontically treated incisors with 2 mm ferrule height.
评估不同根管治疗后技术对冠修复的中切牙疲劳寿命和生物力学行为的影响。
将69颗牛的中切牙牙冠截断，对牙根进行根管治疗，并随机分为三组（n = 23）：树脂复合体桩核修复（BUP）、玻璃纤维桩 - 树脂复合体桩核修复（GFP）和铸造桩核修复（CPC）。对它们进行全冠预备，形成2 mm的箍效应，并用粘结剂粘结白榴石增强陶瓷全冠。每组取三个样本进行单调测试。其余样本在咀嚼模拟器中进行逐步应力疲劳测试，直至在1.5×10⁶次循环后发生断裂或停止测试。采用Kaplan - Meier和Mantel - Cox（对数秩检验）统计分析每个样本失效时的载荷和步数，随后进行多重两两比较，显著性水平为5%。对测试的三组（BUP、GFP和CPC）进行三维建模（Rhinoceros 4.0），并使用有限元分析（FEA）以最大主应力（MPa）标准计算结果。
在载荷或循环次数方面，各治疗组之间无统计学差异（Mantel - Cox对数秩趋势检验，X² = 0.015，自由度 = 1，P = 0.901，X² = 3.171，自由度 = 1，P = 0.995）。冠部裂纹是主要的失效模式，仅在GFP组和CPC组中观察到斜行根折。在有2 mm箍效应的根管治疗后的中切牙中，根管治疗后处理对疲劳寿命无显著影响。不可修复性骨折仅发生在用桩修复的牙齿中。
尽管实验室研究的临床意义存在一些局限性，但本研究表明，对于箍效应高度为2 mm的根管治疗后的中切牙，无桩的树脂复合体桩核修复可能是一种修复选择。
