Fig. 2

SEM Images of enamel surface in each group. Images with 2%, 4%, 6%, 8%BAG groups (a–d), DDW (e), sound enamel (f), demineralized enamel (g) at 10,000 × magnification. All BAG groups a–d showed a precipitation layer covering, while 6% BAG showed the most dense and integrated surface. Microporosities could be seen (white circle) in 2%BAG (a), 4%BAG (b), 8%BAG (d) group. Exposed enamel prisms (red arrows) could be seen in DDW (e) with a large number of pores (white circle). Thin and partial sediments found in (e) could be due to the re-deposition of dissolved Ca and P ions caused by remineralization solution. Regarding sound enamel (f), obvious scratches (white arrow) induced by polishing can be seen. After demineralization, abundant exposed enamel prisms with keyhole patterns could be seen (g), and no deposits were formed