Effects of Different Post Curing Times and Methods on Fracture Resistance and Flexural Strength of 3D-Printed...

The aim of the present in-vitro study was to evaluate the effect of various post-curing times (15, 30, and 45 minutes) and conditions (dry and glycerin-immersion) on the mechanical properties of a permanent crown resin used for 3D-printing.

Crowns (n=90) and bars (n=90) were fabricated using a permanent crown resin (Saremco Crowntec) with a 3D printer (Nextdent 5100) in accordance with the manufacturer's recommendations. After washing with alcohol, the printed specimens were divided into 6 groups (n=15). Post-curing (LC-3DPrint Box) was performed under dry and glycerin- immersion conditions for 15, 30 and 45 minutes. A universal testing machine was used to measure the fracture resistance of crowns and the flexural strength of bars in a three-point bending test. Statistical analysis was performed using independent t-tests and one-way ANOVA (α =.05).

Fracture resistance was not significantly different between the dry and glycerin- immersion groups (P ˃ .05). Flexural strength significantly decreased in the glycerin-immersion specimens, compared with the dry ones in the 15-minute post-cured group (P < .05). Fracture resistance increased, in accordance with the increment in the post-curing time, in both dry and wet conditions, even though no significant difference was obtained for post-processing times of longer than 30 minutes (P ˃ .05). In the glycerin-immersion group, flexural strength increased with post-curing time, showing a significant difference between 15 and 45 minutes (P < .05).

Post-curing time and conditions influence the mechanical features of the investigated 3D printed permanent crown material. The increment of the post-curing time had a favorable influence on the material's mechanical properties.