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

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.

Flexural strength of 3D-printed nanocomposite provisional resins: Impact of SiO2 and ZrO2 nanoparticles and printing orientations in vitro

PURPOSE

The aim of this study was to investigate and compare the influence of zirconium dioxide nanoparticles (ZrO2 NPs) and silicon dioxide nanoparticles (SiO2 NPs) addition and printing orientation on the flexural strength (FS) of provisional three-dimensional (3D) printing resins undergoing thermal cycling (TC).

METHODS

Three dimensional-printed resin (NextDent C&B MFH) was used to fabricate 300 bar-shaped specimens (25 × 2 × 2 mm3 ). The ZrO2 NPs and SiO2 NPs specimens were divided into two groups, then subdivided into three groups, based on the nanoparticle concentration (i.e., 0 wt% (original group), 0.5 wt%, and 1 wt%). Each concentration was printed in three printing orientations (0°, 45°, and 90°). The printed specimens were exposed to 5000 cycles of TC, followed by a three-point bending test to assess the FS. Fracture surface analysis was conducted by using a scanning electron microscope (SEM). For data analysis, ANOVA and Tukey's post hoc were utilized (α = 0.05).

RESULTS

Compared to the original material, the addition of ZrO2 NPs and SiO2 NPs had a significantly positive impact on the FS, (P > 0.001). After TC, the FS of the original group decreased significantly and had the lowest value. The highest FS value was observed in 1% ZrO2 NPs at 0°. Regardless of the nanoparticle concentration, the 0° orientation consistently showed a higher FS, compared to the 45° and 90° orientations. At all orientations (i.e., 0°, 45°, and 90°), the FS significantly increased with the addition of NPs, compared with that of the original material (P > 0.001). TC had a significantly negative effect on the FS of the unmodified groups. However, no significant differences existed in FS among the modified groups after TC.

CONCLUSION

The addition of SiO2 NPs and ZrO2 NPs increased the FS of the 3D-printed provisional resin. Regardless of the nanoparticle concentration, the 0° orientation had the higher FS. TC had an effect on the original resin, whereas it had no significant effect on the nanoparticle-modified resins. In clinical practice, 3D-printed provisional nanocomposite resins printed at the 0° orientation could be recommended for long-term dental provisional restorations.