Stereolithography-based additive manufacturing of lithium disilicate glass ceramic for dental applications.

With additive manufacturing (AM) on the rise in industrial production, different industries are looking for a way to benefit from the advantages over conventional manufacturing methods like milling or casting. The layer by layer approach allows the parallel construction of different complex structures with simultaneous customization of the parts, while waste material is significantly reduced. This is especially interesting for the processing of advanced ceramic materials, where often customized and single parts are required. Regarding ceramics, Lithographic Ceramic Manufacturing (LCM) provides the highest surface quality and achievable precision compared to any other AM technologies, which is necessary to meet the high demands from dental industry regarding accuracy and reproducibility. At TU Wien, we achieved expertise in printing different kinds of ceramics and glasses by using specially developed stereolithography printers based on digital light processing (DLP) followed by a thermal debinding and sintering processes. In dental industry, glass ceramic materials are widely used for customized and aesthetic restorations. This work deals with the processing of lithium disilicate via an AM technology, offering highly dense (>99%), full ceramic parts which meet the requirements for the use as dental restorations. With outstanding mechanical properties of over 400 MPa flexural strength, excellent translucency and accuracy, veneers, crowns and even bridges, especially for the anterior tooth area can be reproducibly printed, debinded and sintered.

Stereolithographic Additive Manufacturing of High Precision Glass Ceramic Parts.

Lithography based additive manufacturing (AM) is one of the most established and widely used 3D-printing processes. It has enabled the processing of many different materials from thermoplast-like polymers to ceramics that have outstanding feature resolutions and surface quality, with comparable properties of traditional materials. This work focuses on the processing of glass ceramics, which have high optical demands, precision and mechanical properties specifically suitable for dental replacements, such as crowns. Lithography-based ceramic manufacturing (LCM) has been chosen as the optimal manufacturing process where a light source with a defined wavelength is used to cure and structure ceramic filled photosensitive resins. In the case of glass ceramic powders, plastic flow during thermal processing might reduce the precision, as well as the commonly observed sintering shrinkage associated with the utilized temperature program. To reduce this problem, particular sinter structures have been developed to optimize the precision of 3D-printed glass ceramic crowns. To evaluate the precision of the final part, testing using digitizing methods from optical to tactile systems were utilized with the best results were obtained from micro computed tomography (CT) scanning. These methods resulted in an optimized process allowing for possible production of high precision molar crowns with dimensional accuracy and high reproducibility.