Impact of Nanoparticle Addition on the Surface and Color Properties of Three-Dimensional (3D) Printed Polymer-Based...

This study aimed to evaluate and compare the impact of additives such as ZrO₂ and SiO₂ nanoparticles (ZrO₂NP or SiO₂NP) on the hardness, surface roughness, and color stability of 3D printed provisional restorations. Two hundred samples in total were printed using 3D printed resins (ASIGA, and NextDent). Each resin was modified with ZrO₂NPs or SiO₂NPs in two different concentrations (0.5 wt% and 1 wt%), while one group was kept unmodified (n = 10). Disc-shaped (15 × 2.5 mm) samples were designed and printed in accordance with the manufacturer's recommendation. Printed discs were evaluated for color changes through parameters CIELAB 2000 system (ΔE₀₀), hardness using Vickers hardness test, and surface roughness (Ra) using a noncontact profilometer. After calculating the means and standard deviations, a three-way ANOVA and Tukey post hoc test were performed at α = 0.05. The addition of ZrO₂NPs or SiO₂NPs to ASIGA and NextDent resins significantly increased the hardness at a given level of concentration (0.5% or 1%) in comparison with pure (p < 0.001), with no significant difference between the two modified groups per resin type (p > 0.05). The highest hardness value was detected in 1% ZrO₂NPs with 29.67 ± 2.3. The addition of ZrO₂NPs or SiO₂NPs had no effect on the Ra (p > 0.05), with 1% ZrO₂NPs showing the highest value 0.36 ± 0.04 µm with NextDent resin. ZrO₂NPs induced higher color changes (∆E₀₀), ranging from 4.1 to 5.8, while SiO₂NPs showed lower values, ranging from 1.01 to 1.85, and the highest mean ∆E₀₀ was observed in the 1% ZrO₂NPs group and NextDent resin. The incorporation of ZrO₂NPs and SiO₂NPs in 3D printed provisional resins increased the hardness without affecting the surface roughness. The optical parameters were significantly affected by ZrO₂NPs and less adversely affected by SiO₂NPs. Consequently, care must be taken to choose a concentration that will improve the materials' mechanical performance without detracting from their esthetic value.