Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 21 0 2024 04 08 1 9 Mehran Mapar Department of Restorative Dentistry, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Sara Gholizadeh Department of Restorative Dentistry, Khorasgan Islamic Azad Dental School, Isafan University of Medical Sciences, Isfahan, Iran Mina Moalemnia Department of Restorative Dentistry, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 2022 04 14 2023 07 22 Objectives:  This study assessed the effects of two remineralizing agents namely MI Paste Plus containing casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACFP) and Remin Pro containing hydroxyapatite, fluoride and xylitol (HFX) with/without erbium-doped yttrium aluminium garnet (Er:YAG) and CO2 laser irradiation on demineralized enamel microhardness. Materials and Methods: In this in vitro study, 70 sound human premolars were mesiodistally sectioned, demineralized at a pH of 4.6 for 8 hours, and randomly divided into 7 remineralization groups (n=10): of (I) MI Paste Plus (CPP-ACFP), (II) Remin Pro (HFX), (III) MI Paste Plus+CO2 laser (0.7 W power, 50 Hz), (IV) Remin Pro+CO2 laser, (V) MI Paste Plus+Er:YAG laser (1 W power, 10 Hz), (VI) Remin Pro+Er:YAG laser, and (VII) negative control. The Vickers hardness number of specimens was then measured. The groups were compared by one-way ANOVA and Tukey’s test (α=0.05). Results: The mean microhardness was 319.8±49.9, 325.3±44.6, 359.4±35.7, 296.4±33.7, 319.9±58.1, 358.9±28.4, and 240.0±41.6 kg/mm2 in groups 1 to 7, respectively. The difference in microhardness was significant among the groups (P<0.0001). Pairwise comparisons revealed significant differences in microhardness between all groups (P≤0.03) except between groups 1 and 2, 1 and 5, 2 and 5, and 3 and 6 (P>0.05). Conclusion: Both Remin Pro (containing HFX) and MI Paste Plus (containing CPP-ACFP) can cause enamel remineralization.  MI Paste Plus+CO2 laser irradiation and Remin Pro+Er:YAG laser irradiation were significantly more effective than the application of each remineralizing agent alone. https://fid.tums.ac.ir/index.php/fid/article/view/4435 https://fid.tums.ac.ir/index.php/fid/article/download/4435/2040