Objectives: This study aims to evaluate the effectiveness of topical fluoride application and diode laser-irradiation on the Micro-hardness of demineralized enamel. Materials and Methods: Sixty enamel samples were prepared; Vicker's microhardness was measured at baseline, after demineralization and after treatments. After demineralization the teeth were randomly assigned into four groups (n = 15): group A, no treatment (control), group B fluoride only; group C, combined therapy of fluoride and diode laser 2 watts and group D, combined therapy of fluoride and diode laser 3 watts. A one-way ANOVA and Tukey post-hoc test procedure were performed for statistical analysis. The level of significance was set at a = 0.05 for all tests. Results: No significant differences were seen in the mean VHN between groups at baseline and demineralized stages. The mean VHN of group C&D after treatment was significantly higher than for groups A and B (P < 0.05).  The mean VHN of group B after treatment was significantly higher than group A (P < 0.05).
Conclusion: Diode laser irradiation of the enamel surface increases enamel micro-hardness when used in combination with fluoride application.