Characterization of temporary and permanent 3D-printed crown and bridge resins.

Purpose: The aim of this study was to evaluate the mechanical, surface, and optical properties of two 3D-printed crown and bridge resins (CROWNTEC and Temp PRINT). Additionally, the study assessed the effects of printing orientation and accelerated hydrothermal aging on their mechanical properties.

Materials and methods: Specimens were 3D-printed using digital light processing technology (Asiga MAX™). Mechanical properties, including flexural strength (FS), compressive strength, and fracture toughness (FT), were determined for each material following ISO standards. Three printing orientations (0°, 45°, and 90°) were used for fabricating 3-point bending specimens. Surface hardness was evaluated using a Vickers indenter. Two-body wear tests were conducted using a ball-on-flat configuration in a chewing simulator with 15,000 cycles, and wear depth was measured with a non-contact 3D optical profilometer. Disk-shaped specimens (n = 5/material) were prepared to measure translucency parameter, gloss and light penetration. For gloss measurement, specimens underwent laboratory-machine polishing (4,000-grit abrasive paper) and chairside two-step hand polishing (Top Dent DiaComposite). Posterior composite crowns (n = 10/material) were fabricated and subjected to cyclic fatigue aging (5,000 cycles at Fmax = 150 N) before quasi-static loading to fracture. The microstructure of each material was analyzed using scanning electron microscopy (SEM). Data were statistically analyzed using ANOVA and Tukey's HSD test.

Results: Hydrothermal aging, printing orientation, and material type significantly affected the FS values (p < 0.05). Temp PRINT showed superior FS (129 MPa) and FT (1.3 MPa m^1/2) compared to CROWNTEC (102 MPa, 0.9 MPa m^1/2), particularly at 0° orientation. Gloss measurements revealed no significant differences between materials (p > 0.05) across used polishing systems. SEM analysis demonstrated differences in microstructure between the materials.

Conclusion: Temp PRINT demonstrated superior mechanical performance compared to CROWNTEC, which exhibited higher translucency values. The printing orientation was identified as a critical parameter influencing the mechanical properties and overall performance of 3D printed restorations.