Fig. 6

SEM results for mild, moderate, and severe DF interface fracture after self-etching adhesive strength test (original magnification, 5.00 k × ; scale bar = 10.0 μm): a Fracture interface of mild fluorosis; the enamel of the bonding surface was relatively uniform and dense, a small number of crystals were disorderly arranged, the interspace between the crystals was slightly widened, and a small amount of adhesive remained. b Fracture interface of moderate fluorosis; the enamel was exfoliated under tension lower than that of severe fluorosis. c Fracture interface of severe fluorosis; the surface enamel was severely exfoliated, and even some dentin tubules were exposed. d Normal healthy enamel bonding group as control group