The present study was designed to evaluate and compare the effect of Topacal C-5, a casein phosphoprotein amorphous calcium phosphate formulation and Home care 0.4 % stannous fluoride gel in the prevention and treatment of white spot lesions.The first part of the study compared the effect of Topacal C-5 and stannous fluoride gel in preventing enamel demineralization. Thirty sound premolar teeth were divided into 3 equal groups of tens: Group I was treated with Topacal C-5, Group II was treated with stannous fluoride, and Group III was used as control group and received no treatment. Standard edgewise brackets were bonded to all teeth then the teeth were coated with an acid resistant varnish leaving about 2mm occlusal and gingival to the bracket. The teeth were cycled between artificial saliva and artificial caries solution everyday for 35 days. Polarized light microscope pictures were taken and the depth and area of the demineralized zone was measured and compared statistically. The Topacal C-5 group showed the least depth and area of demineralization compared to the other two groups. The fluoride group also showed some reduction in the depth and area of demineralization compared to the control group. The second part of the study evaluated the effect of Topacal C-5 CPP-CP and stannous fluoride gel in treating white spot lesions. Artificial white spots were induced in 30 sound premolar teeth. The teeth were then divided into 3 groups: Group I was treated with Topacal C-5, Group II was treated with stannous fluoride, and Group III received no treatment and acted as a control group. The teeth were cycled between artificial saliva and caries solution for 4 weeks. Stereomicroscopic pictures were taken and a scoring system was used to evaluate the severity of the white spot lesions after two weeks and 4 weeks. The number of teeth which showed an improvement in the severity of the white spot lesions from the baseline was greater in the group treated with Topacal C-5 than the stannous fluoride and control group although the improvement was not statistically significant.