Effect of thermal aging on a urethane acrylate-based 3D printing resin incorporated with antibacterial quaternary ammonium methacrylate

Abstract

Purpose: This study aimed to determine the impacts of thermal aging on the mechanical properties, biocompatibility, and antibacterial effectiveness of a urethane acrylate-based (UA) 3D printing resin containing dimethylaminohexadecyl methacrylate (DMAHDM).

Methods: DMAHDM was synthesized and incorporated into UA resin at 0.25 wt%, 0.5 wt%, 0.75 wt%, and 1 wt%. Specimens were 3D printed, washed, post-cured, and thermal cycled at 5 °C and 55 °C for 833, 2500, and 5000 cycles. The group without DMAHDM or aging was considered as the control group. Degree of conversion (DC), color differences, antibacterial effectiveness, cell viability, and mechanical properties were evaluated. Two-way analysis of variance was performed with a significance cutoff of α = 0.05.

Results: DC increased with the DMAHDM concentration, with the highest DC being observed at 1 wt% (53.68 ± 0.35 %) (mean ± standard deviation). The color of the specimens showed significant changes after 2500 and 5000 cycles. Antibacterial effectiveness was improved with 0.75 wt% and 1 wt% DMAHDM. Cytotoxicity was observed with prolonged thermal aging cycles. Flexural strength decreased with increasing DMAHDM concentrations and aging, with the lowest values at 1 wt% (93.02 ± 17.96 MPa) after 5000 cycles. However, Vickers hardness significantly increased with both DMAHDM and aging, reaching a peak at 5000 cycles (24.49 ± 0.96 HV).

Conclusions: DMAHDM concentration and thermal aging significantly influenced UA-based 3D printing resins properties. Higher DMAHDM concentration enhanced antibacterial effectiveness and Vickers hardness yet reduced flexural strength after 0.75 wt%. Thermal aging decreased flexural strength while improving DC and hardness. Prolonged aging also led to color changes and increased cytotoxicity.