To evaluate the surface roughness and color stability of 3D-printed polymethyl methacrylate resin at three printing orientations following polishing and coating: An in vitro study.

Aim: This study delves into how different printing orientations following polishing and coating affect surface roughness and color stability, aiming to refine fabrication methods and enhance patient satisfaction.

Study setting and design: Twenty-seven polymethyl methacrylate (PMMA) resin samples were designed with dimensions of 10 mm × 2 mm and were 3D printed with three different printing orientations (0°, 45°, and 90°), followed by support removal and polishing. After the evaluation, the samples were coated with the layer of PMMA resin.

Materials and methods: Standard tessellation language files as the basis for sample preparation were generated using the Autodesk Meshmixer software and exported to 3D printer for the AM of the specimens. The samples underwent assessment for surface roughness and color stability, forming the three groups with different printing orientations. Subsequently, each sample was coated with unpolymerized PMMA resin and polymerized with ultraviolet light, forming the other three groups following coating. After this process, the samples were reevaluated for surface properties, forming the basis of the study's six distinct groups.

Statistical analyses used: The data was tabulated and evaluated for the mean and the standard deviation.

Results: Upon statistical analysis, the surface roughness of 3D printed polished PMMA resin polished and coated PMMA resin for all printing orientations (P < 0.001). The surface roughness was highest at a 45° angle, followed by 90°, with the lowest roughness observed at 0°. Similarly, in polished and coated PMMA resin, roughness was significantly higher at 45° compared to 0° and 90° but no significant difference between 0° and 90° (P > 0.05). For the color stability parameter, color change (∆E) values showed no significant difference for the three printing orientations (P > 0.05) and among the six study groups.

Conclusions: Different printing orientation markedly affects surface roughness and color stability, while coating with PMMA resin had significantly reduced the surface roughness without a significant impact on color stability. Thus, meticulous selection of printing orientation is essential for achieving desired surface properties.