Lysozyme And Glycine Guiding Amorphous Calcium Phosphate To Remineralize Demineralized Enamel

Objective It is an important goal of modern stomatology to control the progress of caries and restore the beauty,strength and function of teeth through the method of remineralization.It is a hot issue in the field of biomimetic mineralization that hydroxyapatite crystals can be remineralized in order to restore the structure and mechanical properties similar to those of natural enamel on the surface of demineralized enamels.In order to simulate the biomineralization process of natural enamel(amelogenin),the lysozyme(LZM)was used to simulate amelogenin to stabilize the amorphous calcium phosphate(ACP)to form LZM/ACP nanoparticles.In order to simulate the decomposition of enamel in vivo by metalloproteinase,we degraded lysozyme with sodium hypochlorite,and finally ACP nanoparticles were produced.Under the guidance of glycine(Gly),ACP nanoparticles can be arranged in order,from amorphous to order-shaped apatite crystals,so that the surface of etched enamel can be remineralized.Methods1.LZM-ACP nanoparticles were formed by LZM stabilized ACP,and morphologic characteristics of LZM-ACP nanoparticles were characterized by TEM.SAED was used to characterize the morphology and crystallographic properties of the crystal samples in situ.2.Enamel sections were prepared from the caries-free and cracked free mandibular vertical impacted teeth.They were randomly divided into 4 groups(acid-etched enamel group-A,LZM-ACP group-B,LZM-ACP+Gly group-C,natural enamel group-D,each group include10 samples).Anhydrous and oil-free gas was used to dry enamel(group A-C),37% phosphoric acid gel acid etched enamel for 30 s,a large amount of deionized water was washed to remove phosphoric acid,and the enamel surface was dried to chalk color by the air gun.Group D(natural teeth)take non-acid etching as control group.Group A: enamel pieces after acid etching were soaked in artificial saliva(5m L/sample);group B: acid etched enamel pieces after LZM/ACP+Na Cl O treatment were soaked in artificial saliva(5m L/ sample);Group C: acid etched enamel pieces after LZM/ACP+Na Cl O treatment were soaked in Artificial saliva with Gly(5m L/ sample);Group D: natural teeth were mineralized in artificial saliva(5m L/ sample)without any treatment.The enamel of the above groups were mineralized for 3 days and 7 days,respectively.XRD was used to analyze the diffraction pattern of the crystal to determine the atomic and molecular structure of the crystal.The surface morphology of the samples was observed by SEM.EDX-Mapping was used to analyze the qualitative and quantitative analysis of the elements,and the chemical composition of the samples could be analyzed in order to detect the effect of remineralization of the etched enamel.Results1.Lysozyme and ACP can form LZM/ACP nanoparticles by stabilizing high concentration calcium and phosphorus ions in solution.2.In the artificial model of enamel caries in vitro,LZM/ACP nanoparticles were decomposed by Na Cl O,and ACP nanoparticles were deposited on the surface of acid-etched enamel rapidly and orderly,imitating the process of degradation of amelogenin by metalloproteinases in vivo.3.The morphology and structure of the surface re-mineralized layer are similar to that of the natural enamel.Conclusion lysozyme can stabilize the amorphous calcium phosphate.Under the decomposition of Na Cl O,the surface of the acid etched enamel is remineralized by the guidance of glycine.This process is based on the non-classical crystallization theory.It provides a promising method for clinical minimally invasive treatment of early caries.