Natural bone has the capacity for self-repair when the defect is small. However, the body needs artificial support to restore the missing structure once the defect exceeds a critical size. Artificial bone replacement is designed to regenerate the damaged material by mimicking natural bone tissue as closely as possible in structure and mechanics. The implant acts as a replacement for the missing endogenous bone and must be able to withstand the applied loads, which include the handling of the implant before and during surgery as well as the stresses from the patient's daily activities. Bone ingrowth, vascularisation, nutrient transport and waste removal are facilitated by structural similarities such as a degree of porosity.

Since every patient, and therefore every bone defect, is unique, additive manufacturing (AM) has great potential for personalised and customised medicine. We use digital light processing (DLP) based vat polymerisation, which selectively cures photopolymers filled with ceramic powders layer by layer. The high resolution of the process enables a precise replication of the patient's complex anatomy.

Hydroxyapatite or tricalcium phosphate ceramics have impressive properties such as osteoconductivity or osteoinductivity and bioresorbability. However, they have poor mechanical properties and can only be used for small bone replacement implants. Zirconia, on the other hand, has high compressive and flexural strength and is also biocompatible. We therefore fabricated pieces of hydroxyapatite and tricalcium phosphate in combination with zirconia to evaluate the properties of the combined product. We investigated the suitability for DLP-based vat polymerisation and analysed the sintered parts regarding mechanical properties and microstructure.