Fig. 3.

(a-e) SEM photo of unetched enamel surface showing a relative smooth surface whith prism cores. b SEM photo of the enamel surface pattern after etching for 2 min with 15 % HCl showing dissolution of the prism core and an intact prism periphery; c) surface pattern after etching for 2×2 min with 15 % HCl showing little dissolution of the prism core and the periphery; d) surface pattern after etching for 3*2 min with 15 % HCl showing dissolution of the prism periphery; e) surface pattern after etching for 4*2 min with 15 % HCl showing destruction of the enamel prisms core and periphery