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. Author manuscript; available in PMC: 2017 Mar 1.
Published in final edited form as: Acta Biomater. 2015 Dec 31;32:264–274. doi: 10.1016/j.actbio.2015.12.038

Figure 4.

Figure 4

Figure 4

Crack growth resistance of the enamel. a) Representative crack growth resistance curve (R-curve) for the longitudinal direction in an old specimen. The quantities Ko, Kg, Kc represent the initiation, growth and fracture toughness, respectively. b) A comparison of the crack growth resistance in the longitudinal direction for young and old specimens. c) A comparison of the crack growth resistance in the transverse direction for young and old specimens. The dashed line demarcates the mean fracture toughness of the old specimens.