Effects of incorporating magnesium oxide and zirconium dioxide nanoparticles in acrylic resin denture base material: a comparative study.

Objectives: The current study aimed to evaluate the effects of incorporating magnesium oxide (MgO) and zirconium oxide (ZrO₂) nanoparticles individually or in combination into heat-cured acrylic resin on the polymer structure, density, surface roughness, hardness and flexural strength for denture base applications.

Materials and methods: A total of 280 samples were produced and divided into seven groups (n = 10) according to the percentage of nanomaterial used: pure heat-cured samples (control group) and heat-cured samples containing nanoparticles at 0.5 wt.% MgO, 1 wt.% MgO, 0.5 wt.% ZrO₂, 1 wt.% ZrO₂, 0.5 wt.% MgO-ZrO₂, and 1 wt.% MgO-ZrO₂. Polymer chemistry, density, surface roughness, hardness and flexural strength of the tested groups were determined using Fourier transform infrared (FTIR) spectroscopy, the Archimedes method, a profilometer, a microhardness test and a universal testing machine respectively.

Results: The results indicated that both the MgO and ZrO₂ nanoparticles interacted primarily with the carbonyl oxygen atoms, leading to the formation of coordination and ionic bonds. This interaction enhanced crosslinking within the polymer matrix. Additionally, the density of the heat-cured acrylic resin increased in a dose-dependent manner when the nanoparticles were incorporated. The surface roughness decreased with increasing nanoparticle concentration, and the smoothest samples were reported with 1% MgO-ZrO₂. The modified group, which included 0.5% MgO-ZrO₂, exhibited the greatest surface hardness. However, compared with those of the control group, the hardness values notably decreased as the concentration of nanoparticles increased. This reinforcement also significantly improved the flexural strength when the amount of nanoparticles increased.

Conclusions: MgO and ZrO₂ nanoparticles strengthen the polymer matrix by forming coordination bonds with carbonyl oxygens, increasing crosslinking. This increased the density and flexural strength while reducing the surface roughness but lowered the hardness at elevated concentrations. These findings suggest the potential for tailored polymer applications, improved denture performance, increased patient comfort, and longer-lasting dental prostheses.