Yan Jiahau, Taskonak Burak, Platt Jeffrey A, Mecholsky John J
Department of Restorative Dentistry, School of Dentistry, Indiana University, USA.
J Biomech. 2008;41(6):1253-9. doi: 10.1016/j.jbiomech.2008.01.015. Epub 2008 Mar 6.
Dentin, the mineralized tissue forming the bulk of the tooth, lies between the enamel and the pulp chamber. It is a rich source of inspiration for designing novel synthetic materials due to its unique microstructure. Most of the previous studies investigating the fracture toughness of dentin have used linear-elastic fracture mechanics (LEFM) that ignores plastic deformation and could underestimate the toughness of dentin. With the presence of collagen (approximately 30% by volume) aiding the toughening mechanisms in dentin, we hypothesize that there is a significant difference between the fracture toughness estimated using LEFM (Kc) and elastic-plastic fracture mechanics (EPFM) (KJc). Single-edge notched beam specimens with in-plane (n=10) and anti-plane (n=10) parallel fractures were prepared following ASTM standard E1820 and tested in three-point flexure. KJc of the in-plane parallel and anti-plane parallel specimens were found to be 3.1 and 3.4 MPa m 1/2 and Kc were 2.4 and 2.5 MPa m 1/2, respectively. The fracture toughness estimated based on KJc is significantly greater than that estimated based on Kc (32.5% on average; p<0.001). In addition, KJc of anti-plane parallel specimens is significantly greater than that of in-plane parallel specimens. We suggest that, in order to critically evaluate the fracture toughness of human dentin, EPFM should be employed.
牙本质是构成牙齿主体的矿化组织，位于牙釉质和牙髓腔之间。由于其独特的微观结构，它是设计新型合成材料的丰富灵感来源。先前大多数研究牙本质断裂韧性的实验都采用了线弹性断裂力学（LEFM），这种方法忽略了塑性变形，可能会低估牙本质的韧性。由于胶原蛋白（约占体积的30%）有助于牙本质的增韧机制，我们推测，使用LEFM估算的断裂韧性（Kc）和弹塑性断裂力学（EPFM）估算的断裂韧性（KJc）之间存在显著差异。按照美国材料与试验协会标准E1820制备了具有面内（n = 10）和反平面（n = 10）平行断裂的单边切口梁试样，并进行三点弯曲试验。面内平行试样和反平面平行试样的KJc分别为3.1和3.4 MPa m1/2，Kc分别为2.4和2.5 MPa m1/2。基于KJc估算的断裂韧性显著大于基于Kc估算的断裂韧性（平均32.5%；p < 0.001）。此外，反平面平行试样的KJc显著大于面内平行试样的KJc。我们建议，为了严格评估人类牙本质的断裂韧性，应采用EPFM。
