In Vivo Remineralization Of Dentin Using An Agarose Hydrogel Biomimetic Mineralization System

Background Dental hard tissue,both the enamel and the underlying dentin,cannot self-heal if damaged.Currently,a novel cell-free agarose hydrogel biomimetic mineralisation system loaded with calcium and phosphate was successfully developed for regenerating dental hard tissue in vitro in the previous studies.These methods have provided the potential for tooth defect repair via a self-healing mechanism,which is a much more ideal for use in dentistry clinics than the current traditional treatment measures.The hydrogel biomimetic mineralisation system showed a potential clinical use for self-repairing tooth surface defects,such as erosion,wear,caries,and dentin hypersensitivity.Objective The cell-free agarose hydrogel biomimetic mineralization strategies have been confirmed to be capable of regenerating enamel-like or dentin-like tissue microstructures in vitro.The biomimetic remineralization process occurred on the surface of a clean,polishing,and acid-etched tooth piece.The surroundings of the biomimetic mineralization system in vitro are quite different from the complex oral environment.To investigate the real effect of the agarose hydrogel biomimetic mineralisation system in the changeable and complex oral environment,an animal model in vivo was established to explore its potential clinical translation.Methods Firstly,New Zealand White rabbits aged 3 months and weighing average2.25 kg were included in this study.The enamel of the labial surface of rabbits' incisor was removed and the dentin was etched and exposed to oral environment.Secondly,maxillary incisors were used as the experimental groups for biomimetic remineralisation.The mandibular incisors were used as the control group.A 2 mm thick layer of Ca Cl₂ hydrogel film was first placed onto the labial surface of maxillary incisors,and kept to gelification.Then,a transparent polymer custom tray filled up with2 mm thick layer of Na₂HPO₄ hydrogel was covered onto the Ca Cl₂ hydrogel and combined well.The application of mineralisation kept stable and lasted for 8 h daily?defined as a cycle?.The mandibular incisors of the control group were exposed to oral environment directly without any Ca Cl₂ gel or Na₂HPO₄ hydrogel on the tooth surface.Finally,after the one and three cycles,the rabbits were killed,and the front teeth of the experimental and control groups were extracted and evaluated by scanning electron microscopy,X-ray diffraction,and nanoindentation test.Results The regenerated tissue on the dentin surface was composed of highly organised hydroxyapatite?HA?crystals.Densely packed along the c axis,these newly precipitated HA crystals were perpendicular to the underlying dental surface with a tight bond.The demineralized dentin was remineralized.The dentinal tubules were occluded by the grown HA crystals.The nanohardness and elastic modulus of the regenerated tissue were similar to natural dentin.Conclusion The results indicated a potential clinical use for repairing dentin-exposed related diseases,such as erosion,wear,and dentin hypersensitivity.