Liu Ting, Huang Yinghao, Li Yue, Meng Jiali, Liu Yajing, Wei Yuan, Huang Yequan, Zhou Qian, Yang Weidong, Yan Fuhua, Wang Xiang, Zhu Yanan
Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China.
Present address: Department of Endodontology, Nanjing Stomatological Hospital, No. 30 Central Road, Nanjing, China.
BMC Oral Health. 2025 Jan 7;25(1):31. doi: 10.1186/s12903-024-05122-8.
To compare the stress distribution and crack propagation in cracked mandibular first molar restored with onlay, overlay, and two types of occlusal veneers using two different CAD/CAM materials by Finite Element Analysis (FEA).
A mandibular first molar was digitized using a micro CT scanning system in 2023. Three-dimensional dynamic scan data were transformed, and a 3D model of a cracked tooth was generated. Finite element models of four different models (onlay, overlay, and two types of occlusal veneer restored teeth) were designed. Two different CAD/CAM materials, including Lava Ultimate (LU) and IPS e.max CAD (EMX), were specified for both models. Each model was subjected to three different force loads on the occlusal surfaces. Stress distribution patterns and the maximum von Mises (VM) stresses were calculated and compared.
Compared to the base model, all restorations showed that high-stress concentration moved from the lower margin of the crack area towards the top of the crack area. The EMX-restored onlay, overlay, and occlusal veneer 2 had the lower stress in the cracked area and the lower average von Mises stress levels at the lower margin along the cracked line, especially under the 225N lateral force (P < 0.05). The occlusal veneer 1 filled with resin had a poorer stress distribution and higher stress concentration of stress at the remaining crack than the occlusal veneer 2 without resin filled inside.
The EMX restorations with onlay, overlay, and occlusal veneer 2 showed lower stress concentration at the lower margin of crack surface compared to the LU-restored models. The occlusal veneer with internal resin filler exhibited higher stress on the end of the lower margin of the crack surface.
Our results suggest that onlay, overlay ceramic restorations and occlusal veneer (without resin filling inside) may be a favorable method to prevent further crack propagation.
A protocol was specified and registered with the Chinese Clinical Trial Registry (ChiCTR) on 2022-04-12 (registration number: ChiCTR2200058630).
通过有限元分析（FEA）比较使用两种不同CAD/CAM材料制作的高嵌体、覆盖体和两种咬合面贴面修复下颌第一磨牙时的应力分布及裂纹扩展情况。
2023年使用微型CT扫描系统对下颌第一磨牙进行数字化处理。对三维动态扫描数据进行转换，生成有裂纹牙齿的三维模型。设计了四种不同模型（高嵌体、覆盖体和两种咬合面贴面修复牙齿）的有限元模型。为两种模型指定了两种不同的CAD/CAM材料，包括Lava Ultimate（LU）和IPS e.max CAD（EMX）。每个模型在咬合面上承受三种不同的力载荷。计算并比较应力分布模式和最大von Mises（VM）应力。
与基础模型相比，所有修复体均显示高应力集中从裂纹区域的下缘向上缘移动。采用EMX修复的高嵌体、覆盖体和咬合面贴面2在裂纹区域的应力较低，沿裂纹线在下缘处的平均von Mises应力水平也较低，尤其是在225N侧向力作用下（P < 0.05）。填充树脂的咬合面贴面1的应力分布较差，在剩余裂纹处的应力集中高于内部未填充树脂的咬合面贴面2。
与采用LU修复的模型相比，采用EMX修复的高嵌体、覆盖体和咬合面贴面2在裂纹表面下缘的应力集中较低。内部填充树脂的咬合面贴面在裂纹表面下缘末端的应力较高。
我们的结果表明，高嵌体、覆盖体陶瓷修复体和咬合面贴面（内部未填充树脂）可能是防止裂纹进一步扩展的有利方法。
2022年4月12日制定了一项方案并在中国临床试验注册中心（ChiCTR）注册（注册号：ChiCTR2200058630）。
