Background Enamel decalcification in orthodontics is a conc for dentists and methods to remineralize these lesions are the focus of intense research.The aim of this study was to evaluate the remineralizing effect of casein phosphopeptide amorphous calcium phosphate(CPP-ACP)nanocomplexes on enamel decalcification in orthodontics.Methods Twenty orthodontic patients with decalcified enamel lesions during fixed orthodontic therapy were recruited to this study as test group and twenty orthodontic patients with the similar condition as control group.GC Tooth Mousse,the main component of which is CPP-ACP,was used by each patient of test group every night after tooth-brushing for six months.For control group,each patient was asked to brush teeth with toothpaste containing 1100 parts per million(ppm)of fluoride twice a day.Standardized intraoral images were taken for all patients and the extent of enamel decalcification was evaluated before and after treatment over this study period.Measurements were statistically compared by t test.Results After using CPP-ACP for six months,the enamel decalcification index(EDI)of all patients had decreased;the mean EDI before using CPP-ACP was 0.191±0.025 and that after using CPP-ACP was 0.183±0.023,the difference was significant(t=5.169,P＜0.01).For control group,the mean EDI before treatment was 0.188±0.037 and that after treatment was 0.187±0.046,the difference was not significant(t=1.711,P＞0.05).Conclusion CPP-ACP can effectively improve the demineralized enamel lesions during orthodontic treatment,so it has some remineralization potential for enamel decalcification in orthodontics.