Fig. 2
From: Investigation on the Gradient Nanomechanical Behavior of Dental Fluorosis Enamel
SEM images of the normal tooth enamel, mild dental fluorosis enamel, and severe dental fluorosis enamel. The a–c outer layers, d–f middle layers, and g–i inner layers were etched with 37% phosphoric acid for 30 s and then visualized under × 5000 magnification. Green arrows indicate broadened gaps between the enamel rods, while white circles indicate pores. Red arrows indicate loosely arranged crystals in the enamel rods with increasing crystal clearance and micropores