Effects of Agents on the Properties of Water-Washable 3D-Printed Resin

Objectives: This study aimed to investigate the influence of washing agents and washing time on the mechanical and biocompatibility properties of water-washable three-dimensional (3D) printing crown and bridge (C&B) resin.
Methods: Different washing agents (water, detergent, and alcohol) were applied to process the 3D printed specimens under different washing time points (5, 10, 20, and 30 min). Then, the specimens were evaluated for flexural strength, Vickers hardness, degree of conversion (DC), biocompatibility, and monomer elution.
Results: After prolonged washing, the alcohol group exhibited the largest decrease in flexural strength and Vickers hardness, dropping to 52.45±7.40 MPa and 10.14±2.12 GPa after 30 min, respectively. DC in the water and detergent groups showed upward trends after 10 min, peaking at 53.94±1.40% after 20 min and at 54.20±2.59% after 30 min, respectively. Conversely, the DC decreased to 42.42±2.2 % after 30 min of washing in the alcohol group. After 20 min, cell viability in the water group increased to 99.08±4.22%, which was not significantly different from the alcohol and detergent groups. Only triethylene glycol dimethacrylate (TEGDMA) monomer in the non-treatment (NT) group was detected at a specific concentration of 135 ppm.
Conclusions: First, the mechanical properties of the resin weaken with increasing washing time. Water and detergent washing agents are better than alcohol for preserving the mechanical properties during an extended washing process. Second, the DC increases with the washing time when using water and detergent dilutions, whereas it decreases when alcohol is used. Third, increasing the washing time significantly improves cell viability for resin washed with water. After 20 min of washing, there was almost no significant difference in the cell viability of the resins washed using different washing agents. Fourth, resin polymer releases different amounts of monomers for different washing agents and times, with no simple linear relationship between them.