Impact of silicon dioxide and hydroxyapatite nanoparticles on the flexural strength and surface properties of 3D-printed denture base resins: An in vitro study

Abstract

Purpose: This study aims to evaluate and compare the effect of the addition of two nanoparticles (silicon dioxide [Si-NPs] and hydroxyapatite [HA-NPs]) on the flexural strength and surface properties of three-dimensionally (3D)-printed denture base materials. Materials and Methods: In this study, Si-NP and HA-NP were added separately to two 3D-printed resins (ASIGA DentaBASE and NextDent Denture 3D+). The percentage of each nanoparticle was optimized at 0.25 and 0.50 wt%, with 3D-printed resins without nanoparticles (unmodified) as control groups. The specimens were thermally aged (5000 cycles at 5°C and 55°C). The flexural strength test of each group was conducted according to the ISO 20795-1:2013 specifications. After flexural strength, the fractured samples were analyzed under a scanning electron microscope (SEM). The surface roughness and Vickers microhardness tests were performed on disc-shaped (15 × 2 mm) samples. Data analysis was performed using ANOVA followed by Tukey's post hoc test at α = 0.05. Results: The flexural strength was significantly increased with the addition of Si-NPs to ASIGA resin (p < 0.001), while there was no significant increase with Si-NP addition to NextDent resin. The highest flexural strength value (106.75 ± 8.59 MPa) was observed for 0.5% Si-NPs/ASIGA. The flexural strength was significantly decreased (p < 0.001) for both resins with the addition of two percentages of HA-NPs. The surface roughness was significantly reduced (p < 0.001) for both Si-NPs-based groups and 0.25%-based HA-NPs, whereas 0.50% HA-NPs/ASIGA showed the highest surface roughness value (0.46 ± 0.19 µm). Nonsignificant change in microhardness value was observed, whereby the NextDent group showed the highest values compared with ASIGA. Conclusion: Overall, Si-NP had a positive impact on 3D-printed resins, resulting in an increase in flexural strength and a reduction in surface roughness compared to the HA-NP-based groups. However, no difference was observed in the microhardness testing.