*Article* **The Effect of Salinized Nano ZrO<sup>2</sup> Particles on the Microstructure, Hardness, and Wear Behavior of Acrylic Denture Tooth Nanocomposite**

**Kawkb M. El-Tamimi <sup>1</sup> , Dalia A. Bayoumi <sup>2</sup> , Mohamed M. Z. Ahmed 3,4,\* , Ibrahim Albaijan <sup>3</sup> and Mohammed E. El-Sayed <sup>1</sup>**


**Abstract:** The wear of acrylic denture teeth is a serious problem that can change the vertical dimensions of dentures. This study evaluates the effect of adding salinized nano ZrO<sup>2</sup> particles on the microstructure, hardness, and wear resistance of acrylic denture teeth. Heat polymerizing polymethyl methacrylate resin was mixed with salinized ZrO<sup>2</sup> at concentrations of 5 wt.% and 10 wt.%. Acrylic resin specimens without filler addition were used as a control group. SEM/EDS analyses were performed and the Vickers' hardness was evaluated. Two-body wear testing was performed using a chewing simulator with a human enamel antagonist. After subjecting the samples to 37,500 cycles, both height loss and weight loss were used to evaluate the wear behavior. The microstructural investigation of the reinforced-denture teeth indicates sound nanocomposite preparation using the applied regime without porosity or macro defects. The addition of zirconium oxide nanofillers to PMMA at both 5% and 10% increased the microhardness, with values of up to 49.7 HV. The wear mechanism in the acrylic base material without nanoparticle addition was found to be fatigue wear; a high density of microcracks were found. The addition of 5 wt.% ZrO<sup>2</sup> improved the wear resistance. Increasing the nanoparticles to 10 wt.% ZrO<sup>2</sup> further improved the wear resistance, with no microcracks found.

**Keywords:** nanocomposite; acrylic denture teeth; nano ZrO<sup>2</sup> particles; wear behavior; microstructure; microhardness; polymerization; polymethyl methacrylate resin
