Dental caries is the most common chronic disease of childhood. For a long time it has been thought of as an irreversible process, that is initially detected by cavitation. Nowadays, however, it is known that the caries process is mainly alternation of demineralizing and remineralizing cycles that is undergone by the mineralized tooth structures, which can be detected in an earlier phase than the cavity, the white spot lesion. The rationale that deals with preventing dental caries, stopping its progression and remineralizing these non-cavitated lesions, is known as Minimal Intervention Dentistry.The current study was conducted to compare between different concentrations of n-HA solutions, 1%, 5%, 10% and 15%, and determining the optimal concentration for remineralization of initial carious lesions on prepared enamel samples, against a positive control (NaF) and a negative control (DDW).Samples used for this study were created from human premolars extracted due to orthodontic reasons and stored in 0.1% thymol solution till further used. The premolars were cut longitudinally in mesio-distal direction then polished. Buccal surfaces (group A) were separated from lingual ones (group B), (n=15). The samples of each group were further divided into six sub-groups (n=15) according to the treatment solutions. Sub-groups:•Sub-group 1: 1% n-HA solution.•Sub-group 2: 5% n-HA solution.•Sub-group 3: 10% n-HA solution.•Sub-group 4: 15% n-HA solution.•Sub-group 5: NaF solution (positive control).•Sub-group 6: DDW (negative control).