**5. Conclusions**

As mentioned in the introduction and in the discussion, previous studies show that β-TCP is a performing bone replacement material, not only as pure material and shaped by conventional methods (e.g., freeze drying) but also as composite material (e.g., with polymers) and shaped by additive manufacturing. The resulting compressive strength is always relatively low, ruling out load-bearing clinical indications/bone defects. In contrast, our results show that we can address load-bearing bone defects using the same material as previously reported, by advancing known composites to become complexly shaped structural composites that not only unite the structural features of a real bone (dense and porous sections) but also reach similar and improved compressive strengths (of trabecular bone [44,45]), while at the same time providing degradability as given by the material. By fine-tuning the support structure design and working on composite materials to develop new structural and material composites for potential bone replacements, we might be able to further develop mechanical properties, aligning our approach with a variety of bone defects, especially long-bone and load-bearing ones. Offering the same biocompatibility, the bioceramic hybrid foams have significant mechanical advantages over the Curasan benchmark. The hybrid's failure load is 91 times higher in comparison to the commercially available β-TCP ceramic. To summarize, the compressive strength of the bone-mimicking hybrid bones was significantly enhanced, while high biocompatibility was maintained as proven on the Curasan material. At present, the BMBF-funded project "Hybrid-Bone" (03VP07633) is in progress, which builds on these results and strives for the evaluation and validation of materials, processes and hybrid scaffolds for use as compressive-strengthenhanced biodegradable jaw-bone replacements. Within the framework of this project, the comprehensive bone-forming performance tests of similar scaffolds, with a focus on hybrid foams, are carried out in animal models. The authors hope to report on these results soon.

**Author Contributions:** Conceptualization, M.A.; Data curation, M.A., S.H.L., C.S., C.F., D.W., E.S.-F. and M.S.; Investigation, C.F., D.W. and E.S.-F.; Methodology, M.A. and H.O.M.; Project administration, M.A.; Software, C.F.; Supervision, M.A.; Validation, S.H.L., C.S., C.F., D.W. and E.S.-F.; Visualization, S.H.L. and M.S.; Writing—Original draft, M.A.; Writing—Review and editing, M.A. and M.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The animal study (file number 47/18) was reviewed and approved by the Landesdirektion Leipzig, Germany. The approval date was January 15th in 2019 and the study was conducted according to Directive 2010/63/EU.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** This contribution originally was intended to be published together with Anke Bernstein, for Musculoskeletal Biomaterials of the Research Center for Tissue Replacement, Regeneration and Neogenesis (G.E.R.N.) and the Deputy Director of the G.E.R.N in the Department of Orthopaedics and Trauma Surgery at the University Hospital Freiburg in Breisgau, Germany. With our deepest regrets, Anke died in a mountaineering accident at the end of June 2021. Bernstein's research revolved around biomaterials-based therapies for repair and regeneration of musculoskeletal tissues. Bernstein was a dedicated member of the German Society for Biomaterials and held the role of the President since 2019. Anke, you will be remembered as a friendly person with a sharp mind, a great sense of humor and lots of laughter. Thank you, indeed, for walking some of the way together. We offer Anke Bernstein's family, friends and colleagues our sincere condolences on her passing. Many thanks as well to Melanie Lynn Hart for spell-checking this contribution.

**Conflicts of Interest:** The authors declare no conflict of interest.

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