Effect of Printing Layer Thickness and Postprinting Conditions on the Flexural Strength and Hardness of a 3D-Printed Resin.

BACKGROUND

Recently, dentists can utilize three-dimensional printing technology in fabricating dental restoration. However, to date, there is a lack of evidence regarding the effect of printing layer thicknesses and postprinting on the mechanical properties of the 3D-printed temporary restorations with the additive manufacturing technique. So, this study evaluated the mechanical properties of a 3D-printed dental resin material with different printing layer thicknesses and postprinting methods.

METHODS

210 specimens of a temporary crown material (A2 EVERES TEMPORARY, SISMA, Italy) were 3D-printed with different printing layer thicknesses (25, 50, and 100 m). Then, specimens were 3D-printed using DLP technology (EVERES ZERO, DLP 3D printer, SISMA, Italy) which received seven different treatment conditions after printing: water storage for 24 h or 1 month, light curing or heat curing for 5 or 15 minutes, and control. Flexural properties were evaluated using a three-point bending test on a universal testing machine (ISO standard 4049). The Vickers hardness test was used to evaluate the microhardness of the material system. The degree of conversion was measured using an FT-IR ATR spectrophotometer. Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test ( ≤ 0.05).

RESULTS

The 100 m printing layer thickness had the highest flexural strength among the other thickness groups. As a combined effect printing thickness and postprinting conditions, the 100 m with the dry storage group has the highest flexural strength among the tested groups (94.60 MPa). Thus, the group with 100 m thickness that was heat cured for 5 minutes (HC 5 min 100 m) has the highest VHN value (VHN = 17.95). Also, the highest mean DC% was reported by 50 m layer thickness (42.84%).

CONCLUSIONS

The thickness of the 100 m printing layer had the highest flexural strength compared to the 25 m and 50 m groups. Also, the postprinting treatment conditions influenced the flexural strength and hardness of the 3D-printed resin material.