The effect of post-processing washing time on the physical and chemical properties of 3D printable resin materials

This study aimed to evaluate the effects of post-processing washing time on the mechanical properties (flexural strength, Vickers hardness) and chemical properties (water sorption, water solubility, degree of conversion, and elution of residual monomers) of different 3D printable resin materials.

Two different 3D printable resin materials were used: Formlabs 3D Permanent Crown (F) and Saremco Print Crowntech (S). Washing procedures were applied to the control groups according to each manufacturer's instructions and to the experimental groups with increasing washing times (T₁ = 2 × 3 min, T₂ = 2 × 5 min, and T₃ = 2 × 10 min). A total of 296 specimens were evaluated for flexural strength (FS), Vickers hardness (VH), water sorption (Wsp), water solubility (Wsl), degree of conversion (DC), elution of residual monomers (RM) and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) was used for element analysis and surface characterization. Two-way ANOVA test was used for analyses, and Tukey test was used for post-hoc.

No significant differences were found in pairwise comparisons of FS values. (p > 0.05). VH values were significantly higher in the F resin material than in the S resin material at all washing times (p < 0.001). No significant interaction was found between resin type and washing time (p = 0.255), and Wsp values were not significantly different between materials (p = 0.639). A significant interaction was found between resin type and washing time for Wsl (p < 0.001), indicating material-dependent effects. No significant differences in DC values were observed between materials or washing times (p > 0.05). Residual monomer release was significantly influenced by both the resin type and the washing duration, especially for BPA, TEGDMA, UDMA, and Bis-GMA (p < 0.05).

Washing time and resin type influenced specific physical and chemical properties of the materials. A 2 × 5 min (T₂) washing protocol appears optimal for the F resin material, balancing mechanical integrity with reduced monomer release, while longer washing time for S resin material did not provide additional benefits.