Comparing the mechanical and optical properties of different 3D printed resin-based ceramic materials for permanent restoration

Abstract

The utilization of Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) in dentistry has seen a significant increase, resulting in subtle yet impactful changes for clinicians, technicians, and patients. Patients are now more inclined towards faster and more comfortable dental treatments. Consequently, the combined use of intra-oral scanning and dental 3D printing resins for temporary fixed prostheses is becoming a trend. To improve the strength of these resins for creating permanent restorations, scientists have begun incorporating ceramics into the resins. This study aims to compare the mechanical and translucency properties of five different market brands (i.e., Bego VarseoSmile Crown Plus (BG), Detax FREEPRINT Crown (DT), NextDent CrownTec (ND), SprintRay Ceramic (SC), and SprintRay OnX (SO)), all of which claim their products can be used for permanent restorations.

Fifteen specimens were prepared for the three-point bending test (3PB), biaxial flexural tests (BFS), and compressive tests (CS). Post-test images were captured using a Scanning Electron Microscope (SEM). Six samples per brand, with varying thickness (1.0, 1.5, and 2.0 mm), were prepared for the indentation Vickers’s hardness test (HVIT). An equal number of specimens were also prepared for L*a*b* coordinates to measure the Translucent Parameter (TP) and colour differences (ΔE). The samples for hardness and TP tests were measured at baseline and after different thermocycling (1000, 3000, and 6000 cycles) with a dwell time of 30 seconds between the water baths at 5°C and 55°C. Statistical analysis was conducted using One-way ANOVA for 3PB, BFS, and CS results, and 3-Way ANOVA at α=0.05 for HVIT and TP tests.

The One-Way ANOVA indicated that BG had a statistically significant difference (p<0.05) compared to others in both 3PB and BFS tests. However, there was no statistically significant difference among the brands in the compressive test. In the HVIT test, as thickness increased, Vickers’s hardness number (VHN) and elastic modulus also increased. These results also happened after thermocycling except SC. In terms of translucency, the results suggested that as the thickness of the specimen increased, translucency decreased. The number of thermocycles also negatively affected translucency.

The average mechanical values (3PB, BFS, CS) of the sample resins are lower than some current restorative materials such as lithium disilicate (LiSi) and zirconia. Numerous parameters can affect the printing results, including the printing angle of the object, post-washing time, post-cure time, and the degree of conversion.

To conclude, while BG showed a statistically significant difference in 3PB and BFS, there was no significant difference in the CS test. Degradation via thermocycling in the translucency test was observed, whereas in the hardness test, the Vickers Hardness Value (VHN) increased after thermocycling. The average values of 3PB, BFS, and compressive tests among the specimens were still significantly lower than traditional full ceramic products such as lithium disilicate and zirconia. Further tests are required to compare these resins with other permanent restorative materials.