Influence of printing procedure and printing axis of dental alloys on dimensional accuracy, surface roughness, and porosity

Abstract

This study aimed to evaluate the printing procedure and printing axis and its influence on the dimensional accuracy, surface roughness, porosity, and strength of 3D-printed dental alloys used in orthodontics prepared using binder jetting (BJ), electron beam melting (EBM), or selective laser melting (SLM). Specimens with a dimension of 50 mm × 12 mm were produced using BJ, EBM, and SLM techniques of dental alloys and were printed either along the X-, Y-, or Z-axis (n = 8 per group). Specimen dimension was chosen according to the ISO standard 6892-1 for tensile strength test specimens. Surface roughness parameters Sa, Sz, Sq, and Ssk were obtained using a 3D laser microscope and porosities were visualized with scanning electron microscopy (SEM). The specimen surfaces were optically scanned and volumetric deviations from the original stereolithography files were calculated. Afterward, tensile strength was measured. The printing method and printing axis significantly affected surface roughness parameters (P < 0.05). Overall, the lowest surface roughness Sa values were found for BJ (9.1 ± 3.4 µm) followed by SLM (39.8 ± 24.2 µm) and EBM (50.4 ± 6.4 µm). BJ showed the smallest dimensional deviation followed by EBM and SLM. SEM analysis revealed a porous structure of BJ while fewer pores were observed on EBM and SLM samples. The ultimate tensile strength was only determined for BJ (495 ± 6 MPa) and EBM (726 ± 50 MPa) as the strength of SLM superseded the strength of the holder of the universal testing machine. BJ printing provides the highest dimensional accuracy with the smoothest surfaces irrespective of the printing axis. However, the remaining porosities owed to this printing procedure may have decreased the strength of the material.