Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 22 0 2025 12 09 5345 5345 Zahra Jowkar Oral and Dental Disease Research Center, Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Mohammad Mahdi Abdolinezhad Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Seyed Ahmadreza Hamidi Department of Oral and Maxillofacial Surgery, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Ali Moaddeli Legal Medicine Research Center, Legal Medicine Organization, Tehran, Iran 2024 09 08 2025 07 16 Objectives: This study aimed to investigate the effects of incorporating zinc oxide nanoparticles (ZnONPs) and mesoporous ZnONPs into resin-modified glass ionomer cement (RMGIC) on diametral tensile strength (DTS) and flexural strength (FS). Materials and Methods: A total of 70 RMGIC specimens were fabricated and randomly divided into 7 groups (n=10 per group). Group 1 served as the control group. Groups 2 to 4 contained 3wt.%, 5wt.%, and 7wt.% ZnONPs, respectively, and groups 5 to 7 had 3wt.%, 5wt.%, and 7wt.% mesoporous ZnONPs, respectively. ZnONPs and mesoporous ZnONPs were homogeneously incorporated into the RMGIC powder. Disc-shaped (for DTS) and bar-shaped (for FS) specimens were fabricated according to ISO standards. All specimens were stored in distilled water at 37°C for 24 hours before testing. The DTS was measured using a diametral compression test, and the FS was measured by a three-point bending test using a universal testing machine. Data were analyzed by one-way ANOVA and Tukey’s post-hoc test (alpha=0.05). Results: Statistically significant differences were observed in the DTS and FS among the groups (P< 0.001). The 5wt.% mesoporous ZnONPs group exhibited the highest DTS and FS values. The group with 7wt.% ZnONPs showed the lowest DTS and FS values (P<0.05). Conclusion: Incorporation of 5wt.% mesoporous ZnONPs into RMGIC significantly improved its DTS and FS, suggesting that this concentration offers optimal reinforcement of mechanical properties. https://fid.tums.ac.ir/index.php/fid/article/view/5345 https://fid.tums.ac.ir/index.php/fid/article/download/5345/2187