Statement of problem

The preparation design and fabrication materials directly affect the clinical success of endocrown restorations, and yet, knowledge is lacking about the biomechanical impact of specific designs or materials on endocrown restorations.

Purpose

The purpose of this in vitro and finite element analysis study was to evaluate the biomechanical behavior of endocrown restorations.

Material and methods

A total of 36 freshly extracted mandibular first molars were collected. The teeth were prepared as per 2 different preparation geometries: with the buccal wall intact (Class 2) and without the buccal wall (Class 3). Teeth were restored with endocrowns made from 3 different fabricating materials, Vita Enamic, GC Cerasmart, and Lava Ultimate. To analyze the in vitro fracture strength, cemented endocrowns were loaded in a universal test machine with a 200-N oblique force until the restoration fractured. Finite element analysis was used to evaluate the stress distribution on both the dentin tissue and the restorative materials. The data were analyzed with a 2-way ANOVA test and the Tukey post hoc test (α=.05).

Results

No significant differences were found between the different preparation designs (Class 2 and Class 3) on fracture strength (P>.05). The highest mean ±standard deviation fracture strength values were found in the Lava Ultimate material (Class 2, 606.20 ±293; Class 3, 659.40 ±226 N) (P>.05), but the lowest fracture strength test values were obtained in the Vita Enamic material (Class 2, 439.60 ±136; Class 3, 340 ±98 N) (P>.05) for both preparation design test groups.

Conclusions

A statistically significant difference was not found between the 2 tooth preparation classifications. However, significant differences were observed among the test groups in the Class 2 preparation specimens. The Class 2 preparation design exhibited a higher number of irreparable failures.

中文翻译：

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用不同的制备设计和各种修复材料制作的牙冠修复体的 3 维有限元和体外分析

问题陈述

制备设计和制造材料直接影响牙冠修复体的临床成功，然而，缺乏关于特定设计或材料对牙冠修复体的生物力学影响的知识。

目的

这项体外和有限元分析研究的目的是评估牙冠修复体的生物力学行为。

材料与方法

共收集了 36 颗新鲜拔出的下颌第一磨牙。根据 2 种不同的制备几何形状制备牙齿：完整的颊壁（2 级）和没有颊壁（3 级）。使用由 3 种不同制造材料（Vita Enamic、GC Cerasmart 和 Lava Ultimate）制成的牙冠修复了牙齿。为了分析体外断裂强度，将粘合的内冠以 200-N 的斜力加载到万能试验机中，直到修复体断裂。有限元分析用于评估牙本质组织和修复材料上的应力分布。使用 2 向方差分析检验和 Tukey 事后检验 (α=.05) 分析数据。

结果

不同的制备设计（2 级和 3 级）在断裂强度上没有发现显着差异 ( P >.05)。在 Lava Ultimate 材料中发现了最高的平均 ± 标准偏差断裂强度值（2 级，606.20 ±293；3 级，659.40 ±226 N）（P >.05），但最低断裂强度测试值是在Vita Enamic 材料（2 级，439.60 ±136；3 级，340 ±98 N）（P >.05）用于两个制剂设计测试组。

结论

在 2 种牙齿预备分类之间没有发现统计学上的显着差异。然而，在 2 类制备样品中，在测试组之间观察到显着差异。2 类准备设计表现出更多的不可修复的故障。