Effects of Curing Protocols on Physico-mechanical Properties of 3D Printed Resins

Objectives: 3D printed resins consist in a low-cost option for the fabrication of temporaries in the dental office offering integration with the digital workflow. Nevertheless, the recommended post-processing time using curing chambers makes its use inviable for chairside use. The present study assessed the effects of different curing protocols on the physico-mechanical properties of 3D printed resins.
Methods: Ten discs (8mm diameter x 2mm thickness) and 20 bars (2x2x8mm) were used for each resin group (Denture Teeth/DT, Formlabs; Crown and Bridge/CB, Nextdent; Cosmos Temp/CT, Yller), assessing color stability (after 7days in dry, dark storage; and after 24h artificial aging in water at 60°C) using a spectrophotometer (Vita Easyshade V); and flexural resistance (24h after curing and after 10,000 thermal cycles) using a 3-point bending test. Each sample was cured using: 1) Formcure curing chamber/FC during 30 minutes at 80°C; 2) Custom made curing chamber/CCC during 30 minutes at 50°C; 3) Valo light curing (Ultradent) during 40s/V40; and 4) Valo during 120s/V120. Data was analyzed using 3-way ANOVA (flexural resistance) and 2-way repeated measurements ANOVA (color stability).
Results: CB showed the highest color stability, followed by DT/CT. All curing protocols showed similar results, except by V40 (higher color change) for DT/CT, and V120 (lowest color change) for DT. V120 yielded similar or higher flexural strength values than Formcure. V40 was equivalent to CCC and both showed lower results than the other groups. Considering the same curing protocol, all resins showed similar flexural strength. After artificial aging, a decrease in flexural resistance was observed only for CB cured using Formcure and V120; although still corresponding to the highest observed flexural resistance after aging for this resin.
Conclusions:
Valo light curing unit can be used as a curing protocol for 3D printed resins with similar or enhanced physico-mechanical properties when compared with curing boxes.