Three-dimensionally printed denture base resins modified with green-synthesized TiO2 nanoparticles: A multiparametric assessment

Abstract

Statement of problem

Three-dimensionally (3D) printed denture base resins offer advantages in digitally assisted dentistry but still show inferior mechanical performance and color stability compared with conventional and milled resins. Green-synthesized titanium dioxide nanoparticles (TiO₂NPs) may provide improved dispersion and reduced agglomeration compared with chemically synthesized forms, potentially enhancing the performance of printed resins.

Purpose

The purpose of this in vitro study was to evaluate the effect of incorporating TiO₂NPs, green-synthesized utilizing grape seed extract (GSE-TiO₂NPs), on the biaxial flexural strength (BFS), Weibull reliability, microhardness, surface roughness, and color stability of a 3D printed denture base resin before and after thermocycling.

Material and methods

GSE-TiO₂NPs were synthesized, transmission electron microscope (TEM)-characterized, silanized, and incorporated into a printable denture base resin at 0.5 wt% and 0.75 wt%. Disk specimens were 3D printed and assigned to control, 0.5 wt% TiO₂, and 0.75% TiO₂ groups. BFS (n=24/group), Vickers microhardness, surface roughness, and color difference (ΔE00) (n=12/group) were evaluated before and after 600 thermocycles (between 5 °C and 55 °C). The data were analyzed using a statistical software program (jamovi v2.6.44). BFS was analyzed using robust ANOVA (20% trimmed means, bootstrap CIs) with robust post hoc tests. Microhardness and surface roughness were evaluated using linear mixed-effects models with Bonferroni-adjusted post hoc tests. The Mann-Whitney U test was used for color change assessment, and the Kruskal-Wallis test, followed by the Dunn post hoc test with Bonferroni correction were used to compare the percentage and ∆E change among groups (α=.05).

Results

TEM showed quasispherical nanoparticles (mean size 11.8 nm). Increasing TiO₂NP concentration produced a significant rise in BFS (P<.001), with values increasing from 51.73  ±2.56 MPa (control) to 73.58  ±4.73 MPa (0.75%) before aging. After thermocycling, reinforced groups maintained significantly higher BFS, and the control showed the greatest percentage reduction (–16.46%). Weibull analysis demonstrated higher characteristic strength and reliability in the 0.75 wt% group before and after aging. Microhardness increased in a concentration-dependent manner (control: 16.92  ±0.79 VHN; 0.75%: 23.08  ±0.79 VHN; P<.001), and reinforced groups exhibited less reduction after thermocycling. Surface roughness increased significantly with nanoparticle incorporation but remained well below the clinical threshold (0.2 µm). Color change values remained clinically acceptable across groups (ΔE00<4.1, the clinically acceptable threshold).

Conclusions

Green-synthesized GSE-TiO₂NPs at 0.5% and 0.75% enhanced the BFS, microhardness, and failure reliability of 3D printed denture base resin, maintaining acceptable roughness and color stability. Improved dispersion and reduced agglomeration support a sustainable, effective reinforcement strategy for durable denture bases.