Abstract: Objective　 Using the laser cavity detection system DYAGNOdent(DD) to compare the effects of Duraphat and Fluor Protector on inhibition of enamel demineralization after fixed orthodontic appliance during three-months. Methods　In our department, 60 teenagers with straight-wire appliance were enrolled in the study, including 23 males and 37 females, aged 12-18 years with a mean of 14.8 years. This experiment adopted the self-control method. The right upper anterior teeth and premolars were given Duraphat as experimental group A, and the left lower anterior teeth and premolars were given Fluor Protector as experimental group B；The left upper anterior teeth and premolars did not receive any special treatment as control group A, and the right lower anterior teeth and premolars were given normal saline as control group B. Before bonding brackets, and 1 and 3months after bonding brackets, totally 3 times, the degree of enamel demineralization was detected by the laser cavity detection system, DIAGNodent. (DD).One-way ANOVA analysis was used to compare enamel demineralization whether there was statistical significance.Results　 (1)The DD detection values of the two experimental groups were both significantly lower than that of the control groups at 1 and 3months after bonding brackets, indicating that Duraphat and Fluor Protector could inhibit the enamel demineralization(P<0.05). (2)The DD detection values between experimental A and experimental B while 1 and 3months after bonding brackets showed no significantly difference (P>0.05), indicating that there were no significantly difference between the two kinds of fluoride varnish.Conclusions　(1) The patients with fixed orthodontic treatment are susceptible to enamel demineralization.(2) Duraphat and Fluor Protector with two different concentrations could both inhibit enamel demineralization during orthodontics. There is no significant difference between these two groups in inhibiting demineralization.

Key words: Duraphat, Fluoride varnish, Demineralization