Effect of Direct-Heating-System on Properties of Dental 3D Printing Resin

Objectives: This study aims to evaluate the effectiveness of direct heating methods within a 3D-printed resin tank in inducing resin viscosity changes to exhibit suitable physical properties and accuracy.
Methods: Before printing, a heat transferable Indium Doped Tin Oxide (ITO) glass plate was appended under a commercially available 3D printer resin tank. The heat was transferred to the resin using an external power supply module to achieve desired heating parameters. Specimens fabricated with resin temperatures at 30°C, 40°C, 50°C were evaluated. Control specimens were fabricated without any heat treatment (U/T). The mechanical properties were quantified by Vickers micro-hardness, flexural strength (FS), elastic modulus (EM), and modulus of resilience (MOR) (n=10). In addition, a three-dimensional accuracy analysis of 3D printed crowns (n=4) was conducted. Scan data using the table-top scanner and designed data were compared using 3D morphometric software. One-way ANOVA and Tukey's post hoc test were performed to check the differences between groups.
Results: The temperature of the resin during 3D printing significantly affected the mechanical properties. Significant (p<0.001) differences in micro-hardness between the groups were observed in the order of 30°C (7.66±0.40), 40°C (7.74±0.49), 50°C (6.86±0.72) and U/T (5.68±0.38). Significant (p<0.05) differences were observed in both FS and EM properties. In the 50°C group, the highest FS (90.33±11.56MPa), EM (3618.88±339.73MPa), and MOR (1.14±0.25 MPa) were observed, while U/T had the lowest (FS: 59.24±5.52 MPa; EM: 2526.48±127.58 MPa; MOR: 0.70±0.11Mpa). FS and EM showed differences with increasing temperature; however, MOR differences were not statistically significant. In addition, it was found that the accuracy of the 3D printing was not affected within the heating temperature range used in this study (p=0.019).
Conclusions: Within the same printing conditions of the study, the temperature of the printing resin can have a positive effect on the physical properties of the resin.