Randomized with (1:1) prospective, double-blind, controlled trial. Subjects will be randomized to receive S-PRG and the control group receives ICON.

Interventions: - All the procedures will be performed by the same clinician. DIAGNOdent will be used to assess the fluorescence loss of WSLs and the adjacent sound enamel. WSLs in permanent teeth will be treated according to the manufacturer's instructions with:

• Group I (Control group): 20 teeth will be treated with ICON.
• Group II ( EXPERIMENTAL) : 20 teeth will be treated with PRG BarrierCoat.

Observation: - The treatment methods will be assessed immediately after the intervention, 3 months,6 months, and one year. The data will be collected for evaluation of the difference in color and fluorescence loss between the treatment groups, by using DIAGNOdent devices, over different time intervals.

Ethical considerations: The research protocol is approved by the ethical committee, Faculty of Dental Medicine, Al-Azhar University and the enrolled patients should sign a written consent form.

Inclusion Criteria:

• Patients within 20-40 years of age.
• Each patient has 4 or more WSLs.
• Mild and moderate WSLs according to Gorelick's scale.
• Good oral hygiene and willing patients who can attend the study visits.
• a Symmetrical number of permanent teeth in each arch (mesial to second molars).

Exclusion Criteria:

• Active carious lesions.
• Facial surface restorations.
• Intrinsic and extrinsic stains.
• Patients who have a significant medical history or if they smoke.
• Criteria for discontinuation; Mortality and acquiring severe debilitating disease