The Anisotropic and Inhomogeneous Nature of Additively Manufactured Metals, and the Application of Selective Laser Melting in Dentistry

Abstract

Additive manufacturing of metal represents a powerful pathway to fabricate highly complex parts without the need of special tooling and is best suited if either only low quantities are required, or the case at hand requires a fast fabrication. All of these circumstances are given as far as dental restorations are concerned. Highly customizable geometries are required since every restoration is unique. However, in every instance only one identical piece at a time is needed, and the treatment’s effectiveness benefits from the accelerated preparation of the restorations. This research project has identified significant improvements in additive manufacturing, especially regarding the fabrication of directly deployable components. While there are still numerous challenges to be overcome, the manufacturing capabilities are undergoing a step-change and the undertaken work contributes to this progress. The research efforts in this dissertation were dedicated to understand and describe the anisotropy and inhomogeneity in selective laser melted metal components. The investigations ranged from the inhomogeneity in the surface morphology and quality to the material and direction dependent anisotropy in mechanical properties such as hardness, tensile and compressive strength, as well as fracture toughness. The outcome were descriptions of the material and process conduct dependent anisotropy, with explanations of their origin based on the microstructural development throughout the fabrication process. Moreover, dental grade cobalt-based alloys were fabricated, utilizing the selective laser melting, and the suitability for dental purposes was proven. Furthermore, based on the results clear recommendations are provided on post-heat treatments to achieve isotropic material properties and to further enhance the material properties.