Objective: To evaluate the effects of immediate dentin sealing（IDS） on the dentin surface morphology and the dentin bond strength of teeth with fluorosis. Methods: Forty-eight non-carious teeth with fluorosis extracted due to periodontal disease were collected and divided into four groups according to the Thylstrup and Fejerskov index（TFI）:normal group（TFI = 0）

mild group（TFI = 1 ～ 3）

moderate group（TFI = 4 ～ 5）

and severe group（TFI = 6 ～ 9）. Each group was further divided into two subgroups:control group and intervention group. The dentin surface was treated with normal saline in the control group

and with IDS in the intervention group. For every group

one sample was observed by a scanning electron microscope

and the remaining samples received bonding of a composite resin block（4 mm × 4 mm × 3 mm） to the surface of dentin and then microtensile bond strength testing. Results: The mean tensile bond strength of the IDS groups was significantly higher than that of the control groups（F =46.01

P < 0.001）. The tensile bond strength significantly decreased as the severity of dental fluorosis increased（F =35.77

P < 0.001）. According to electron microscopy

the sealing rate of dentin tubules and the number and length of resin tags decreased with the increasing severity of dental fluorosis

regardless of treatment modalities;the sealing rate and the quality of resin formation were significantly better in the IDS groups than in the other groups. Conclusion: IDS can effectively improve the dentin sealing rate and dentin bond strength of teeth with fluorosis

but the bond strength decreases with the increasing severity of dental fluorosis.