Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

The challenge of endodontic regeneration is modulated by clinical conditions which determine five kinds of tissue requirements: pulp connective-tissue formation, dentin formation, revascularization, reinnervation and radicular edification. Polymer scaffolds constitute keystone of the different endodontic regenerative strategies. Indeed, scaffolds are crucial for carrying active molecules and competent cells which optimize the regeneration. Hydrogels are very beneficial for controlling viscosity and porosity of endodontic scaffolds. The nanofibrous and microporous scaffolds mimicking extracellular matrix are also of great interest for promoting dentin-pulp formation. Two main types of polymer scaffolds are highlighted: collagen and fibrin. Collagen scaffolds which are similar to native pulp tissue, are adequate for pulp connective tissue formation. Functionnalization by active biomolecules as BMP, SDF-1, G-CSF enhances their properties. Fibrin or PRF scaffolds present the advantage of promoting stem cell differentiation and concomitant revascularisation. The choice of the type of polymers (polypeptide, PCL, chitosan) can depend on its ability to deliver the active biomolecule or to build as suitable hydrogel as possible. Since 2010s, proposals to associate different types of polymers in a same scaffold have emerged for adding advantages or for offsetting a disadvantage of a polymer. Further works would study the synergetic effects of different innovative polymers composition.

The treatment of osteochondral defects remains a challenge. Four scaffolds were produced using Food and Drug Administration (FDA)-approved polymers to investigate their therapeutic potential for the regeneration of the osteochondral unit. Polycaprolactone (PCL) and poly(vinyl-pyrrolidone) (PVP) scaffolds were made by electrohydrodynamic techniques. Hydroxyapatite (HAp) and/or sodium hyaluronate (HA) can be then loaded to PCL nanofibers and/or PVP particles. The purpose of adding hydroxyapatite and sodium hyaluronate into PCL/PVP scaffolds is to increase the regenerative ability for subchondral bone and joint cartilage, respectively. Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) were seeded on these biomaterials. The biocompatibility of these biomaterials in vitro and in vivo, as well as their potential to support MSC differentiation under specific chondrogenic or osteogenic conditions, were evaluated. We show here that hBM-MSCs could proliferate and differentiate both in vitro and in vivo on these biomaterials. In addition, the PCL-HAp could effectively increase the mineralization and induce the differentiation of MSCs into osteoblasts in an osteogenic condition. These results indicate that PCL-HAp biomaterials combined with MSCs could be a beneficial candidate for subchondral bone regeneration.