Figure 2. Fracture toughness of dentin. (a) Fracture resistance data for dentin tested with continuously irrigation in whisky (N = 5), expressed in terms of crack-resistance curves (R-curves), measured on compact-tension, C(T) specimens. Each data point type represents a separate sample. The shaded regions on the R-curves indicate similar data obtained for hydrated dentin and dentin dehydrated in pure ethanol. The bar graphs (mean ± SD) show a significant increase in (b) crack initiation, (c) crack growth and (d) steady-state ("plateau") fracture toughness for dentin dehydrated in whisky and ethanol, as compared to hydrated dentin. Differences in the growth and plateau toughness were statistically significant (p < 0.05).