The Effect of Post-Processing in the Form of Ion Etching in Ar and O Applied to Metallic 3D Prints Produced Using the DMP Method on Their Cleaning Efficiency and Biological Response

Abstract

Direct Metal Printing (DMP) three-dimensional (3D) printing technology, also known as direct laser sintering of metal powders, enables the production of metal components with complex geometries that are not achievable with traditional casting methods or subtractive techniques. The DMP method enables the production of metal objects with high precision. One of the important applications of additive manufacturing is the production of medical implants. A significant challenge in the production of medical devices using DMP technology is the so-called post-processing. An improperly performed postproduction cleaning process may lead to the presence of metal powder particles that were not bound during laser melting. Their presence in the friction pair after implantation, and/or their release into surrounding tissues, may cause accelerated wear and induce inflammatory reactions. The most common drawbacks of widely available and commonly used post-processing methods include their limited effectiveness in removing surface powder residues and a significant loss in volume and mass of the prints. In the second case, the result is a reduction in the mechanical strength of the implant (e.g., with electrochemical methods), and in the first case, there is a risk of inducing an immune response in the body. According to literature reports, regardless of size, at high concentrations in the body (1 × 10⁶ particles/mL), unbound powder particles induce an immune response already at an early stage. Electrochemical methods effectively remove unbound particles, but at the same time cause significant losses in the volume and mass of prints, which affects their strength. This study aimed to improve the quality of 3D-printed implants by cleaning their surfaces of unbound metal particles (post-processing). Comparing the results reported in the literature for various surface treatment methods (chemical, electrochemical, mechanical, plasma), plasma treatment was identified as the most promising solution. Oxygen and argon plasma cleaning was performed at different time periods (1, 2, and 4 h) on sandblasted substrates after production and without this treatment. The study aimed to verify the effectiveness of the plasma cleaning process in removing particles from metallic 3D-printed components and to assess the impact of surface treatments on biological response using an osteoblast cell model.