Sub-10-micrometer toughening and crack tip toughness of dental enamel
Sub-10-micrometer toughening and crack tip toughness of dental enamel
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DOI：
10.1016/j.jmbbm.2010.12.003
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发表时间：
2011-04-01
影响因子：
3.9
通讯作者：
Schneider, Gerold A.
中科院分区：
文献类型：
--
作者：
Ang, Siang Fung;Schulz, Anja;Schneider, Gerold A.
在以往的研究中，牙釉质在体内表现出对小裂缝的咬合迹象，在体外对较大的裂缝表现出r曲线行为。本研究量化了裂纹尖端的韧性（K-I0）。K-III0)、裂纹闭合应力和牙釉质裂纹尖端的内聚区大小，并研究裂纹尖端附近的增韧机制，直至单个牙釉质晶体的长度尺度。采用原子力显微镜（AFM）研究了成熟牛牙釉质上维氏压痕引起的裂纹的裂纹开启位移（COD）分布。沿搪瓷棒边界和跨搪瓷棒裂纹的I型裂纹尖韧性K10表现出相似的取值范围：K- i0，K- Ir = 0.5-1.6 MPa m(0.5)（基于Irwin的“近场”解）和K- i0，K-cz = 0.8-1.5 MPa m(0.5)（基于Dugdale-Muskhelishvili （DM）裂纹模型的内聚区解）。III型裂纹尖端韧性K-III0。Ir，计算为0.02 ~ 0.15 MPa m（0.5）。利用黏结区溶液计算裂纹尖端的闭合应力为163 ~ 770 MPa，黏结区长1.6 ~ 10.1 μ m，黏结区宽24 ~ 44 nm。在原子力显微镜和扫描电镜下观察到增韧元素：蛋白质韧带和羟基磷灰石纤维（微观和纳米尺度）引起的裂缝桥接以及微裂纹。英国皇家版权所有(C) 2010出版的爱思唯尔有限公司版权所有。
In previous studies, enamel showed indications to occlude small cracks in-vivo and exhibited R-curve behaviors for bigger cracks ex-vivo. This study quantifies the crack tip's toughness (K-I0. K-III0), the crack's closure stress and the cohesive zone size at the crack tip of enamel and investigates the toughening mechanisms near the crack tip down to the length scale of a single enamel crystallite. The crack-opening-displacement (COD) profile of cracks induced by Vickers indents on mature bovine enamel was studied using atomic force microscopy (AFM). The mode I crack tip toughness K10 of cracks along enamel rod boundaries and across enamel rods exhibit a similar range of values: K-I0,K- Ir = 0.5-1.6 MPa m(0.5) (based on Irwin's 'near-field' solution) and K-I0,K-cz = 0.8-1.5 MPa m(0.5) (based on the cohesive zone solution of the Dugdale-Muskhelishvili (DM) crack model). The mode III crack tip toughness K-III0.Ir, was computed as 0.02-0.15 MPa m(0.5). The crack-closure stress at the crack tip was computed as 163-770 MPa with a cohesive zone length and width 1.6-10.1 mu m and 24-44 nm utilizing the cohesive zone solution. Toughening elements were observed under AFM and SEM: crack bridging due to protein ligament and hydroxyapatite fibres (micro- and nanometer scale) as well as microcracks were identified. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.