El-Sheikhy Refat, Al-Khuraif Abdulaziz
Dental Biomaterials Research Chair, Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.
Sci Rep. 2024 Oct 8;14(1):23462. doi: 10.1038/s41598-024-73061-z.
Current research introduces understanding of dental-cracks mechanistic with fundamental fracture behavior in natural-teeth and orthodontics including mode I crack under both tension and compression, mode II crack under both clockwise-shear and anticlockwise-shear and mixed-mode cracks under both compression-shear and tension-shear. It depends on experimental models of transparent-Plexiglas including pre-cracks of different orientations angle (b) based on fundamental theoretical fracture analysis with comparison. Problem-concept, cracking aspects of fracture-initiation, propagation-direction, fracture-increment length, critical external-load and fracture path are predicted experimentally and theoretically using directional fracture approach and directional strain-energy density theory. Tests are carried out for (36) samples for compression and tension in LEFM. Friction-resistance between crack-surfaces is considered with derivation of equations and charts. Negative stress-intensity factor (-K) is developed for solving complicated problems of cracks under occlusal compression loads. The occlusal loads are compression and shear producing lateral tensile mixed mode cracks. The critical propagation angle (q), critical propagation load (s) and critical propagation envelope of stress intensity factors (K-K) are developed with respect to crack orientation angle (b) with comparisons. They are necessary to predict the fracture propagation early before teeth-failure. It helps for prevention and control of dental-cracks, correct-restoration, prosthodontics, orthodontics, and development of new dental-materials and technologies.
当前的研究引入了对牙齿裂纹机制的理解，涉及天然牙和正畸学中的基本断裂行为，包括拉伸和压缩下的I型裂纹、顺时针剪切和逆时针剪切下的II型裂纹以及压缩-剪切和拉伸-剪切下的混合模式裂纹。这取决于基于基本理论断裂分析并进行比较的透明有机玻璃实验模型，该模型包括不同取向角（b）的预裂纹。使用定向断裂方法和定向应变能密度理论，通过实验和理论预测了问题概念、断裂起始的裂纹方面、扩展方向、断裂增量长度、临界外部载荷和断裂路径。在LEFM中对36个样本进行了压缩和拉伸测试。考虑了裂纹表面之间的摩擦阻力，并推导了方程和图表。为解决咬合压缩载荷下裂纹的复杂问题，开发了负应力强度因子（-K）。咬合载荷是产生横向拉伸混合模式裂纹的压缩和剪切力。针对裂纹取向角（b），通过比较得出了临界扩展角（q）、临界扩展载荷（s）和应力强度因子的临界扩展包络线（K-K）。它们对于在牙齿失效前早期预测断裂扩展是必要的。这有助于预防和控制牙齿裂纹、正确修复、修复学、正畸学以及新型牙科材料和技术的开发。
