Background: Deciduous teeth is the children’s teeth which already erupted perfectly at the age of 2.5 years as well as serving for the mastication, phonation, esthetic, and supporting periodontal tissues of children. The structure of tooth enamel has a different structure with permanent tooth enamel. Enamel is the outer structure of the teeth in the form of hard tissue that contains hydroxyapatite. Demineralization can occur in email as a result of which the acid can dissolve hydroxyapatite so that the enamel becomes soft. Remineiralization process required for the re-establishment of the missing tooth mineral. Calcium, phosphat, and fluor play a role in the remineralization process. Purpose: This study aims to determine hardness differences of deciduous tooth enamel with TAF and without TAF before and after immersion using milk. Materials and methods: Research design used is an experimental laboratory in vitro. Samples are deciduous anterior teeth post extraction. The study was conducted by giving treatment to each tooth samples each test group. Tooth hardness measured before and after treatment. Result: The results showed that there are signifcant different hardness of deciduous teeth enamel hwith TAF and without TAF after immersion using milk (p<0,05). The tooth enamel without TAF on immersion using milk is harder than the tooth enamel that have been given TAF and soaked with milk.