ZrO₂ and ZnO nanoparticles effect on setting time, microhardness, and compressive strength of calcium-enriched-mixture cement

Aim: Calcium-enriched mixture (CEM) cement is an endodontic biomaterial; however, enhancing its physical/mechanical properties remains a challenge. This in vitro study investigates the influence of zirconium oxide (ZrO₂) and zinc oxide (ZnO) nanoparticles on the setting time, microhardness, and compressive strength of CEM cement. Methods: Four different groups of CEM cement were prepared: a control group without nanoparticles, two groups with ZrO₂ or ZnO, and a group with a combination of nanoparticles. The nanoparticles were added to the powder in predetermined concentrations. The setting time was evaluated using the Gilmore needle method, while microhardness and compressive strength were determined using Vickers hardness and a universal testing machine, respectively. Results: The incorporation of ZnO slightly reduced the setting time, while the addition of ZrO₂ significantly prolonged it compared to the control group. Interestingly, the combination of both nanoparticles exhibited a setting time comparable to that of the control group. Regarding the microhardness and compressive strength, both ZrO₂ and ZnO significantly improved these properties compared to the control group. The combination of both nanoparticles showed the highest microhardness and compressive strength values among all groups. Conclusions: The addition of nanoparticles to CEM cement effectively modifies its physical and mechanical properties. The optimal combination of these nanoparticles can potentially achieve an improved balance between setting time and enhanced mechanical performance.