Time-Dependent Dispersion of TiO₂ Nanoparticles in 3D-Printed Denture Base Resin Using Probe Sonication

Titanium dioxide (TiO₂) nanoparticles (NPs) can improve the performance of 3D-printed denture base resins; however, the reinforcing benefit depends on achieving uniform dispersion, and the effect of probe-sonication time on NP dispersion remains unclear. This study aimed to determine the sonication time (among 3, 5, and 7 min) producing the most qualitatively uniform TiO₂ distribution. TiO₂ NPs were silanized using 3-(trimethoxysilyl)propyl methacrylate, incorporated at 0.3 wt.% into a light-polymerizing 3D-printing resin, and probe sonicated. The resulting specimens were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, and tested for surface roughness (Ra, μm) and Vickers hardness. Qualitatively, increasing sonication time progressively improved dispersion: the 7 min group showed the most homogeneous microstructure and titanium map. FTIR spectra were comparable across the groups, indicating preserved matrix chemistry. Surface roughness and hardness were not significantly different among the groups (p = 0.686 and p = 0.510, respectively). The 7 min group had the most qualitatively uniform TiO₂ distribution. Although it had the numerically lowest surface hardness, it was not comparatively statistically significant. Therefore, within the tested conditions, the 7 min can be described as the most suitable duration for the primary dispersion objective. Additional tests (flexural strength, flexural modulus, and impact toughness) and degree-of-conversion analysis are necessary to confirm the effects of different sonication times.