Fig. 2

Elastic modulus values and topography of enamel and dentin in the three groups, determined by AFM. a Elastic modulus measurement was performed at the same four sites as those of microhardness measurements. a, middle enamel; b, 50 μm from the DEJ in enamel; c, 50 μm from the DEJ in dentin; d, middle dentin. At the site 50 μm from the DEJ in enamel (point b), Young’s modulus values in the 30-Gy and 60-Gy groups were significantly lower than in the control. *p < 0.05. n = 20 in each; ANOVA. b Typical topographic mapping of enamel. With the dose increasing, more diffused enamel prism and impaired interprismatic substance can be seen