Effects of incorporating aluminum oxide nanoparticles on the polymer structure, porosity, surface roughness, and hardness of denture base materials

The present study aimed to evaluate the polymer structure, surface roughness, hardness, and porosity of heat-cured acrylic resin modified with two different concentrations of aluminum oxide (Al 2 O 3 ) nanoparticles. A total of 90 specimens were fabricated and divided into three main groups ( n = 10) according to the test; each group was further divided into three subgroups based on the loading ratio of Al 2 O 3 nanoparticles: heat-cured samples without addition (control group) and heat-cured samples incorporating with Al 2 O 3 nanoparticles at 1 and 2 wt%. The polymer structure, surface roughness, surface hardness, and porosity were assessed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, a profilometer, a Shore D hardness tester, a photomicroscope, and the Archimedes method, respectively. FTIR spectra showed hydrogen bonding between carbonyl groups and Al 2 O 3 nanoparticles, indicating enhanced filler-matrix interactions at higher loadings, the addition of 2 wt% Al₂O₃ improved interfacial adhesion but may increase hydrophilicity, representing a trade-off for applications requiring moisture resistance. Notably, a significant decrease in porosity and surface roughness, along with an increase in surface hardness, was observed in heat-cured acrylic resin containing 1 wt%. Conversely, increasing the nanoparticle loading to 2 wt% increased porosity and surface roughness and decreased surface hardness. These laboratory findings demonstrated that Al 2 O 3 nanoparticles can modify the surface and structural properties of 3D‑printed denture base resins. In particular, the 1 wt% Al 2 O 3 composite showed the best short‑term surface properties.