Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University and Horus University (HUE), Mansoura, Egypt.
Production and Mechanical Design Department, Faculty of Engineering, Mansoura University, Mansoura, 35516, Egypt.
BMC Oral Health. 2023 Jun 25;23(1):421. doi: 10.1186/s12903-023-03114-8.
To assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis.
Forty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05.
In the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively.
Statistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.
通过三维有限元分析评估和比较不同 CAD/CAM 材料对内、边缘间隙、抗压强度和端盖修复体失效概率的影响。
收集 40 颗失活的上颌第一磨牙。根管治疗后，根据端盖制作材料将其分为 4 组（n=10）。组 V（Vita-Enamic）、组 N（Nacera Hybrid）、组 T（Translucent Prettau Zirconia）和组 P（Pekkton ivory）。所有样本均经过人工老化模拟临床服务 1 年的方法处理。利用硅橡胶复制技术和立体显微镜（25X）评估不同区域端盖的边缘和内部间隙。对粘结试件进行抗压强度试验，然后用立体显微镜进行定性研究。为修复严重受损的根管治疗上颌第一磨牙，生成了代表四个端盖系统的四个模型，用于有限元分析（FEA）。施加轴向和中心静态咬合压缩载荷。分别评估剩余牙体结构、粘结线和修复材料上的修正后的 Von Mises 和最大主应力值。在 P 值≤0.05 时对所得数据进行统计学分析。
在本研究中，在所研究的组中，ZrO2 组的内、边缘间隙（μm）的平均值最高（分别为 100.300 和 102.650），而 Nacera 组的内间隙（μm）平均值最低（69.275），PEKK 组的边缘间隙（μm）平均值最低（78.4750）。关于内间隙，Vita-Enamic 和 PEKK 组之间没有统计学上的显著差异（P=0.293），而 ZrO2 和其他测试组之间在边缘间隙区域的平均值上存在统计学上的显著差异（p<0.05）。另一方面，PEKK 组的断裂阻力（1845.20 N）平均值最高，Vita-Enamic 组的断裂阻力（946.50 N）最低。关于三维有限元分析的应力分布，根据修正后的 von Mises（mvM）分析，在与牙体结构、粘结线和可流动复合材料相关方面，PEKK 模型的最大可能应力值最高（分别为 93.1、64.5、58.4 MPa），而 ZrO2 则显示出较低的最大应力值（11.4、13.6、11.6 MPa）。
与其他使用的端盖材料相比，PEKK 在统计学上表现出优异的边缘和内部拟合。此外，PEKK 材料的断裂阻力与氧化锆值相当，而 Vita Enamic 材料的断裂阻力最低。
