Physicochemical and mechanical comparison of denture base materials after artificial aging

This study aimed to evaluate the impact of artificial aging on the surface integrity, mechanical properties, and thermal stability of three commercially available denture base materials: conventional heat-polymerized polymethyl methacrylate (PMMA), CAD/CAM-milled PMMA, and 3D-printed photopolymerizable resin.

Cylindrical samples (6 mm diameter × 3 mm height) were fabricated for each material. All samples were finished, and measurements were performed on the finished flat surface. A total of 20 samples were prepared for each material; half were tested at baseline and half after artificial aging, yielding a final sample size of n = 10 per group. Artificial aging was performed using 5000 thermocycles between 5 °C and 55 °C with a 10-second dwell time. Surface roughness (mean Ra, µm) was measured using non-contact optical profilometry, while surface microhardness (mean Vickers hardness, HV) was assessed using the Vickers hardness test. Thermal stability was evaluated using thermogravimetric analysis (TGA; mass loss, %) and differential scanning calorimetry (DSC; heat flow, mW/mg). Surface morphology was examined through scanning electron microscopy (SEM).

Results indicated a significant increase in surface roughness for all materials post-aging (p < 0.05), with 3D-printed resin showing the greatest change (0.04 → 0.07 μm) and milled PMMA the least (0.04→0.06 μm). Milled PMMA had the highest baseline hardness (20.01 HV) and exhibited the least reduction after aging, while 3D-printed resin experienced the most pronounced decline (16.96→16.21 HV). TGA showed mass gain in conventional PMMA (+ 0.23%) and 3D-printed resin (+ 0.13%), whereas milled PMMA lost mass (-0.16%).

Overall, CAD/CAM-milled PMMA demonstrated superior thermal aging resistance, maintaining hardness and surface quality, followed by conventional PMMA. In contrast, 3D-printed resin was most vulnerable to surface deterioration and softening under artificial aging. CAD/CAM-milled PMMA can be a recommended choice for the denture base.