Hosiptal of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
Hosiptal of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
Comput Methods Programs Biomed. 2022 Nov;226:107178. doi: 10.1016/j.cmpb.2022.107178. Epub 2022 Oct 6.
Post-core-crown (PCC) and endocrown are two common restorative methods for severely damaged molars, but exhibit disadvantages. This study aimed to explore the practicability of modified endocrown with a 2 mm intracanal extension (MED) to restore defective teeth using finite element analysis (FEA).
Five groups of numerical models of mandibular molars restored by three MEDs, a PCC, and a routine endocrown after root canal treatment were devised by FEA software. We constructed 4 mm, 3 mm, and 2 mm thickness of MED restorations to restore mandibular molars that were prepared to 1 mm, 2 mm, and 3 mm from the cemento-enamel junction (CEJ). Furthermore, PCC and routine endocrown were used to compare the stress distribution with MED. Lithium disilicate glass-ceramics (EMAX) and resin nanoceramics (LU) were considered restorative materials, and a vertical load of 600 N and an oblique load of 200 N were applied to the restorations.
In three MEDs by LU, 2 mm thickness of restoration generated the highest stress on prepared teeth, while the thickness of EMAX did not significantly influence the stress value. MED by LU generated higher stress around the CEJ, and reduced the stress on the middle and lower root compared to MEDs by EMAX, PCC by EMAX, and PCC by LU. MED by EMAX caused lower stress around the CEJ, and generated higher stress in the chamber walls after extended root canals compared with MED by LU, endocrowns by LU, and endocrowns by EMAX. There was an evident stress concentration at the last but one layer, which was a thin area of the tooth root in all restorative models.
The use of modified endocrown may be considered an effective restorative method to restore defective mandibular molar, but suitable restorative material must be selected based on the tooth preparation method and deficiencies in the tooth structure.
后牙核-冠（PCC）和髓腔全冠（endocrown）是两种常用于修复严重受损磨牙的方法，但都存在缺点。本研究旨在通过有限元分析（FEA）探讨具有 2mm 管内延伸（MED）的改良髓腔全冠修复牙体缺损的实用性。
使用 FEA 软件设计了经过根管治疗后，用 3 种 MED、PCC 和常规髓腔全冠修复的下颌磨牙的 5 组数值模型。我们构建了 4mm、3mm 和 2mm 厚的 MED 修复体，用于修复从牙釉质牙骨质界（CEJ）预备 1mm、2mm 和 3mm 的下颌磨牙。此外，还比较了 MED 与 PCC 和常规髓腔全冠的应力分布。采用锂硅玻璃陶瓷（EMAX）和树脂纳米陶瓷（LU）作为修复材料，对修复体施加 600N 的垂直载荷和 200N 的斜向载荷。
在 3 种 LU 制成的 MED 中，2mm 厚的修复体对预备牙产生的应力最高，而 EMAX 的厚度并不显著影响应力值。与 EMAX 制成的 MED、PCC 制成的 EMAX 和 PCC 制成的 LU 相比，LU 制成的 MED 在 CEJ 周围产生更高的应力，同时降低了中根和下根的应力。与 LU 制成的 MED、endocrowns 制成的 LU 和 endocrowns 制成的 EMAX 相比，EMAX 制成的 MED 在 CEJ 周围产生的应力较低，但在扩大根管后的腔室壁上产生更高的应力。在所有修复模型中，最后但一层都存在明显的应力集中，这是牙齿根部的一个薄弱区域。
改良髓腔全冠可能是修复下颌磨牙牙体缺损的有效方法，但必须根据牙体预备方法和牙齿结构的缺损选择合适的修复材料。
