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Various artificial bone graft substitutes based on ceramics have been developed over the last 20 years. Among them, calcium-silicate-based ceramics, which are osteoconductive and can attach directly to biological organs, have received great attention for bone tissue engineering applications. However, the degradation rate of calcium-silicate and bone formation is often out of balance, resulting in stress shielding (osteopenia). A new strategy to improve the drawbacks of these ceramics is incorporating trace elements such as Zn, Mg, and Zr into their lattice structures, enhancing their physical and biological properties. Recently, baghdadite (Ca3ZrSi2O9) ceramic, one of the most appealing calcium-silicate-based ceramics, has demonstrated high bioactivity, biocompatibility, biodegradability, and cell interaction. Because of its physical, mechanical, and biological properties and ability to be shaped using various fabrication techniques, baghdadite has found high potential in various biomedical applications such as coatings, fillers, cement, scaffolds, and drug delivery systems. Undoubtedly, there is a high potential for this newly developed ceramic to contribute significantly to therapies to provide a tremendous clinical outcome. This review paper aims to summarize and discuss the most relevant studies performed on baghdadite-based ceramics and composites by focusing on their behavior in vivo and in vitro.

Stem cells are the central element of regenerative medicine (RM). However, in many clinical applications, the use of scaffolds fabricated with biomaterials is required. In this sense, mesoporous bioactive glasses (MBGs) are going to play an important role in bone regeneration because of their striking textural properties, quick bioactive response, and biocompatibility. As other bioactive glasses, MBGs are mainly formed by silicon, calcium, and phosphorus oxides whose ions play an important role in cell proliferation as well as in homeostasis and bone remodeling process. A common improvement of bioactive glasses for RM is by adding small amounts of oxides of elements that confer them additional biological capacities, including osteogenic, angiogenic, antibacterial, anti-inflammatory, hemostatic, or anticancer properties. Moreover, MBGs are versatile in terms of the different ways in which they can be processed, such as scaffolds, fibers, coatings, or nanoparticles. MBGs are unique because their textural properties are so high that they still exhibit outstanding bioactive responses even after adding extra inorganic ions or being processed as scaffolds or nanoparticles. Moreover, they can be further improved by loading with biomolecules, drugs, and stem cells. This article reviews the state of the art and future perspectives of MBGs in the field of RM of hard tissues.