Micro-indentation fracture behavior of human enamel.
OBJECTIVE
The purpose of this study was to determine the crack resistance behavior (K(R)) of human enamel in relation to its microstructure.


METHODS
Human molar teeth were precision cut, polished and tested using Vickers micro-indentation at different loads ranging from 0.98 to 9.8 N. Five indentation load levels were considered, 20 indentation cracks for each load level were introduced on the surface of the test specimen (10 indentations per tooth) and their variability was evaluated using Weibull statistics and an empirical model. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the crack morphology and propagation mechanisms involved.


RESULTS
The results showed that enamel exhibited increasing cracking resistance (K(R)) with increasing load. It was found that the crack propagation mainly depended on the location and the microstructure it encountered. SEM showed the formation of crack bridges and crack deflection near the indentation crack tip. The crack mode was of Palmqvist type even at larger loads of 9.8 N. This was mainly attributed to the large process zone created by the interwoven lamellar rod like microstructure exhibited by the enamel surface.


CONCLUSIONS
This study shows that there are still considerable prospects for improving dental ceramics and for mimicking the enamel structure developed by nature.
Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302735, Republic of Korea.
Sanosh Kunjalukkal
SK
Padmanabhan
Avinash
A
Balakrishnan
Min-Cheol
MC
Chu
Taik Nam
TN
Kim
Seong Jai
SJ
Cho
D000465:Algorithms; D001696:Biomechanical Phenomena; D003743:Dental Enamel / Q000648:ultrastructure*; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D008963:Molar / Q000648:ultrastructure; D008964:Molar, Third / Q000648:ultrastructure; D016008:Statistical Distributions; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000473:pathology*