Abstract
Regenerative therapy in dentistry has gained interest given the complexity to restore dental and periodontal tissues with inert materials. The best approach for regeneration requires three elements for restoring functions of affected or diseased organ tissues: cells, bioactive molecules, and scaffolds. This triad is capable of modulating the processes to replace lost or damaged tissues and restore function, as it has an impact on diverse cellular processes, influencing cell behavior positively to induce the complete restoration of function and morphology of such complex tissues. Hydrogels (HG) have shown advantages as scaffolds as they are soft and elastic three-dimensional (3D) networks formed from hydrophilic homopolymers, copolymers, or macromers. Besides simple or hybrid, HG show chemical, mechanical and biological activities such as the incorporation of cells in their structures, the retention of high-water content which enhances the transportation of cell nutrients and waste, and elastic and flexible characteristics that emulate the native extracellular matrix (ECM). HG can induce changes in cellular processes such as chemotaxis, proliferation, angiogenesis, biomineralization, and expression of specific tissue biomarkers, enhancing the regeneration process. Besides some of them have anti-inflammatory and anti-bacterial effects. This review aims to show an extensive overview of the most used hydrogels in tissue engineering, emphasizing those that are studied for the regeneration of oral tissues, their biological effects, and their clinical implications. Even though most of the HG are still under investigation, some of them have been studied in vitro and in vivo with outstanding results that may lead to preclinical studies. Besides there are HG that have shown their efficacy in patients such as hyaluronan HG that enhances the healing of gingival tissue.
Highlights
In recent years, advances have been made in oral tissue engineering and regenerative dentistry thanks to the growing amount of research in fields such as, stem cell biology, genetic, molecular engineering, and pathologies that affect the dental organ and its supporting tissues (Miran et al, 2016)
Gelatin Methacryloyl (GelMA) has been used for the construction of cell-loaded microspheres for bone regeneration in vivo (Zhao et al, 2016), as multicomposite with polyethylene glycol (PEG), gelatin, and heparin (PGH) scaffold to induce chondrogenesis (Chen et al, 2020), in combination with sodium alginate, and polytethacrylate (PEGTA) as a bio-link to print highly organized and perfusible 3D biologically relevant vessels with significant potential in tissue construct engineering vascularized (Jia et al, 2016). Another HG used is the microbial transglutaminase enzymatically crosslinked gelatin. mTG catalyzes the formation of covalent N e-(g-glutamyl) lysineamide bonds between individual gelatin strands to form a permanent network of polypeptides, creating physiologically biocompatible scaffolds adequate for live surgery procedures, as well as a slow-release HG to deliver antibiotics and prevent bacterial colonization on the surface of implants for orthopedic surgery, as is feasible for intraoperative manipulation and can resist the pressure force in the insertion of intramedullary implants (Yung et al, 2007)
Collagen-based HG have been used as immunomodulators, drug carriers, healing agents, chelators, and in tissue regeneration (Wei et al, 2019). This type of HG can promote adhesion, proliferation, and differentiation in cardiac, corneal epithelial, endothelial, liver, bone, and mesenchymal stem cells (MSCs) (Agmon and Christman, 2016) and have been studied in a Yucatecan mini-porcine model, where the porcine dental pulp stem cells (DPSC) were transferred through the collagen HG directly to the root canal, previously prepared through pulpectomy, after 4 months, the analysis showed that vascularized soft tissue was recovered, creating a structure similar to a dentin bridge covering it
Summary
The best approach for regeneration requires three elements for restoring functions of affected or diseased organ tissues: cells, bioactive molecules, and scaffolds. This triad is capable of modulating the processes to replace lost or damaged tissues and restore function, as it has an impact on diverse cellular processes, influencing cell behavior positively to induce the complete restoration of function and morphology of such complex tissues. This review aims to show an extensive overview of the most used hydrogels in tissue engineering, emphasizing those that are studied for the regeneration of oral tissues, their biological effects, and their clinical implications.
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