Introduction Caries initiation is associated with demineralization of the tooth enamel surface. Calcium and phosphorous are lost from the subsurface enamel, resulting in the formation of a subsurface lesion. Aim: this study aimed to investigate and compare the enamel surface ultramorphology and minerals content by Environmental Scanning Electron Microscope (ESEM) and Energy dispersive x-ray spectroscopy (EDX) and to assess micro-hardness (Vickers test) of demineralized enamel surface treated with CPP-ACP casein Phosphopeptide-Amorphous Calcium Phosphate Flouride(MI Paste Plus) or SDF ( FAgamine). Materials and methods: This study was conducted on twenty eight human premolars ,were collected from the outpatient clinic of Maxillofacial Department, Faculty of Dentistry, Suez Canal University. The selected premolars distributed into three groups: Group I: consisted of 7 intact sound premolars,(control group) Group II : consisted of 7 demineralized premolars,(demineralized group) while, Group III consisted of 14 premolars ( each one divided into 28 halves mesiodistally) then all 28 specimens of group III were demineralized and half of them were treated by MI Paste plus ( subgroup IIIa) and other were treated by SDF( subgroup IIIb). All Groups I,II&III were placed in artificial saliva for 7days at 37ᵒc. Results: There was a statistically significant difference between calcium and phosphorus values of the three groups; subgroup IIIa showed the highest value followed by subgroup IIIb & group I and finally the least value was related to group II .The highest value of fluoride content related to subgroup IIIb. There was not statistically significant difference between microhardness values of group I and group III while group II revealed the lowest microhardness value. Conclusion: Both CPP-ACPF and SDF show areas of mineralized deposits and improvement of enamel ultrastructure. Also both CPP-ACPF and SDF are efficient remineralizing agent, but CPP-ACPF is more efficient as remineralizing agent than SDF. CPP-ACPF shows better microhardness results than SDF.