Optimizing Photoinitiator Concentration in 3D-Printed Resins for Provisional Dental Restorations

The study aimed to evaluate the effect of different TPO photoinitiator concentrations on the mechanical, physicochemical, and biological properties of 3D-printed resins for provisional dental restorations. The resin was formulated with 60 wt.% UDMA, 40 wt.% TEGDMA, 1 wt.% TPO, 0.01 wt.% BHT, and 5 wt.% BaSil. TPO was incorporated at concentrations of 1, 2, and 3 wt.% (TPO1%, TPO2%, and TPO3%, respectively). Specimens were designed using software and printed with an SLA/LCD 3D printer. Post-processing involved ultrasonication in isopropanol followed by UV curing for either 10 or 30 minutes. The resins were evaluated for degree of conversion (DC), flexural strength and modulus, Knoop microhardness, softening in solvent, color stability, and cytotoxicity. No significant difference in DC was observed between TPO1% and TPO3% for both post-polymerization times (p >0.05). TPO3% post-polymerized for 10 minutes exhibited the highest flexural strength and modulus (p <0.05). All groups showed a reduction in hardness after solvent exposure. No statistical difference was found for ΔKHN% (p > 0.05), but post-polymerization time significantly influenced ΔKHN% in the TPO1% group (p < 0.05). Cytotoxicity did not differ significantly among groups (p >0.05). TPO1% post-polymerized for 30 minutes exhibited a color change within clinically acceptable thresholds. The 3D-printed resin with 3% TPO demonstrated significant improvements in mechanical properties, an increased degree of conversion, and no cytotoxic effects. However, it exhibited a significant color change after aging. The 1% TPO group post-cured for 30 minutes showed promising overall results.