Artificial Aging and Its Impact on Surface Properties of Conventional and CAD–CAM Occlusal Splint Materials: An In Vitro Comparative Study

Abstract

Purpose This study aimed to evaluate and compare the surface roughness, microhardness, and color stability of various materials after dry storage (control) and artificial aging (intervention). Materials and Methods One‐hundred‐eight 10 × 10 × 5 mm3 specimens were fabricated from three clear acrylic resin types: heat‐cured (HC), milled (ML), and 3D‐printed (3D). Each specimen underwent a stepwise polishing process on one side. For the pre‐test measurement, 36 specimens (12 per group) were evaluated for surface roughness (Ra), 36 for Vickers microhardness (Vickers hardness number [VHN]), and 36 for color stability (∆E). Half of the specimens in each test were stored in dry conditions for 30 days, while the other half was aged in 37°C distilled water for 30 days. Post‐test evaluations were conducted using the same procedures. The statistical analyses of Ra, VHN, and ∆E were performed using SPSS 29.0. Results Significant differences in Ra were observed among all materials (p < 0.05), with ML and 3D exhibiting low Ra. The artificial aging condition did not significantly influence Ra, however, polishing significantly affected Ra. The VHN values also differed significantly among materials (p < 0.05), with ML demonstrating the highest VHN. Polishing did not affect VHN, but all materials had reductions in VHN (p = 0.002) after artificial aging. The ∆E values varied significantly across material types, with ML demonstrating the least color change. Conclusion This study demonstrated significant variations in surface roughness, microhardness, and color stability among occlusal splint materials after the aging conditions. ML exhibited superior performance with low Ra, low ∆E, and high VHN.