Biomimetic Repair Tooth Enamel And Dentine

Biomineralization is a universal phenomenon in nature,and produces numerous biological nanocomposites,such as bone,teeth and shell,which exhibit excellent mechanical properties.Teeth are the most durable in these biocomposites,which mainly composed of enamel and dentine.Both enamel and dentine are highly mineralized tissues,but their structures and mineral contents are different.In teeth,enamel is the most outer layer,which protects the mammalian tooth from external physical and chemical damage,and dentine locates inner,being weaker but tougher than enamel and to inhibit the crack from enamel to propagate deeply tooth.The mature enamel is acellular,which mainly consists of ribbon-like hydroxyapatite phase(96%by weight),and can hardly self-repair after damage.Currently,caries is one of the most prevalent chronic diseases in humans worldwide.Despite great attempts at enamel remineralization,no full repair of enamel has been achieved since its complicated and hierarchical structure cannot be reproduced.Currently,increasing evidence demonstrate that biomineralization at the growth frontier occurs in an integrated crystalline-amorphous interface:the crystalline mineral phase is coated by its amorphous phase(precursor)to ensure continuous epitaxial construction(e.g.,the continuous crystal growth frontiers of zebrafish fin bone and nacre).Inspired by these biological processes,we rationally designed materials composed of calcium phosphate ion clusters(CPICs)can result in a precursor layer with a continuous mineralization interface that induced epitaxial crystal growth of enamel hydroxyapatite(HAP),which mimics the biomineralization crystal-precursor frontier of hard-tissue development.After full repair,the damaged enamel could be recovered completely and its hierarchical structure and mechanical properties were identical to those of natural enamel.CPICs could be prepared in ethanol solution at large scale,in which the triethylamine(TEA)served as the stabilizer.Different from the polymer,TEA is a small organic molecule that easily volatilizes in ambient environments,inducing CPICs to aggregate and fuse into continuous bulk materials.Therefore,a continuous inteface from enamel crystal to amorphous prescuor can be constructed by using CPICs.Subsequently,the epitaxial crystal growth of enamel HAP crystal replicated the‘fish-scale-shaped' structure precisely,resulting in a 2-3 ?m repaired layer.After repair,the mechanical performance and microtribological behavior sharply similar to these of native enamel.The suggested phase-transformation-based epitaxial growth follows a biomimetic strategy for enamel regeneration and,more generally,for the continuous construction of materials with structural complexity.The CPICs induced the formation of bulk ACP materials with continuity structure due to its small size effect.Hence,the content of CPICs in ethanol was increased,and thus a thicker calcium phosphate repaired layer formed on the enamel surface.The newly formed HAP crystal and original HAP of enamel fused into an entirety.The CPICs-induced ACP transformed into a dense HAP crystal layer completely in remineralization solution and was validated by using confocal laser scanning microscopy.The mechanical properties of repaired enamel were enhanced dramatically because of the formation of the compacted crystal.Biomimetic repair of etched enamel by using CPICs is an effective way,but the involvement of ethanol and TEA during the synthesized process inhibit its implication in clinical therapy of carious,Therefore,the gel-like CPICs,which contains a low level of TEA,was obtained by high-speed centrifuge and redispersed into biocompatible glycerin resulting in toothpaste-like material.Simulating the tooth brushing,the etched enamel was treated with the mixture of simulated oral fluid and CPICs glycerin solution.After ten cycles of treatment,the crystalline HAP crystal obviously deposited on the etched enamel surface,and the mechanical behavior was strengthened because of the formation of mineral.These results demonstrate that the CPICs could be pontentially applied in the prevention and therapy of carious.The polymer-stabilized calcium phosphate nanoclusters could induce the remineralization of dentine collagen.And we found that the adsorbed citrate molecules on collagen fibrils can significantly reduce the interfacial energy between the biological matrix and the amorphous calcium phosphate precursor to enhance their wetting effect,sequentially facilitating the intrafibrillar mineralization.This finding demonstrates the importance of interfacial controls in biomineralization controls and more generally,provides a physicochemical view about the regulation effect of small biomolecules on the biomineralization interface.Based on this new understanding,we could further develop an effective method to remineralize dentine by using citrate.Different from conventional repaired technology,biomimetic repairing enamel and dentine is a new strategy,achiveing remineralization in situ and enhancement of mechanical strength.The experimental results in vitro show that biomimetic mineralization is a very effective tactic,but yet many strategies still cannot be applied in the prevention and therapy of carious.Developing a more effective and could practical strategy for enamel and dentine repair will be a huge challenge and the final target for carious repair.