Hamadan University of Medical Sciences Avicenna Journal of Dental Research 2423-7582 14 1 2022 03 29 In Vitro Effect of Strontium-Doped 45S5 Bioglass and Nd:YAG Laser on Microhardness of Demineralized Enamel 20 24 10.34172/ajdr.2022.04 EN Bahareh Asgartooran Erfan Akbari Loghman Rezaei-Soufi Roya Najafi-Vosough Journal Article 10.34172/ajdr.2022.04 2021 05 29 2021 09 05 Background: This study aimed to assess the effect of strontium-doped 45S5 bioglass (BG) and Nd:YAG laser on the microhardness of demineralized enamel. Materials and Methods: In this in vitro, experimental study, 65 sound enamel samples were prepared of human premolars and polished, and then immersed in a demineralizing solution for 10 weeks. The samples were randomly divided into 5 groups of control, BG, laser, laser plus BG, and BG plus laser. Two samples of each group underwent assessment of surface morphology under a scanning electron microscope. Finally, the microhardness of samples was measured using a Vickers hardness tester, and data were analyzed by ANOVA. Results: The mean microhardness of the BG group was significantly higher than that of other groups (P<0.05). The lowest microhardness was noted in the control group. The difference in microhardness was significant between laser and laser plus BG groups (P<0.05). Further, the BG plus laser group had a significant difference in microhardness with BG and control groups (P<0.05). The difference between laser plus BG and control groups was also significant in this respect (P<0.05). Eventually, maximum morphological changes were observed in the BG group. Conclusions: Overall, BG seems to be effective for the treatment of incipient enamel caries. It effectively increases enamel microhardness and decreases mineral loss while preserving the integrity of the enamel surface.