Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 13 3 2026 10 24 345 351 EN Sara Majidinia Department of Restorative Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Ehsan Baradaran Nasseri Department of Restorative Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Mohammad Hassan Zangane Ebrahimi Student Research Committee, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Mohammad Erfan Khorashadizadeh Student Research Committee, School of Dentistry, North Khorasan University of Medical Sciences, Bojnurd, Iran. Farzaneh Khosravi Department of Cosmetic and Restorative Dentistry, North Khorasan University of Medical Sciences, Bojnurd, Iran. 2026 04 17 2026 08 30 Introduction: This study aimed to investigate the effect of adding 10-MDP monomer to resin-modified glass ionomer on its compressive strength and microhardness.  Materials and Methods: In this experimental study, an acetonic stock solution of 10-MDP was diluted with RMGI liquid to achieve final 10 MDP concentrations of 0%, 5%, 10%, and 15% (w/v). According to ISO 9917-1, compressive strength was evaluated on cylindrical samples with 4*6 mm dimensions (n = 7) by a universal testing machine with a crosshead speed of 1mm/min and a force of 5KN. For hardness measurement, cylindrical samples with dimensions of (2 * 4mm) were prepared for each group (n = 7), and the Vickers hardness test was performed. Data were analyzed by one-way ANOVA, and Tukey’s test (α = 0.05).  Results: There was no significant difference between the groups in terms of compressive strength. The hardness in the RMGI + 10% 10-MDP group was significantly higher than all the studied groups and the control group has a significantly higher average hardness than the RMGI + 15% 10-MDP group.  Conclusion: The addition of 10% (w/v) of 10-MDP to the resin-modified glass ionomer significantly improves its hardness, without affecting its compressive strength. Keywords: Resin modified glass ionomer; 10-MDP monomer; Compressive strength; microhardness. https://jcr.tums.ac.ir/index.php/jcr/article/view/637 https://jcr.tums.ac.ir/index.php/jcr/article/download/637/514