Remineralization Of Demineralized Enamel By Amorphous Calcium Phosphate Guided By Biomimetic Chimeric Peptides

Objectives:Caries are one of the most prevalent oral diseases in the world at present.The process of caries is divided into shallow,middle and deep caries according to the depth of the invasive dental tissue.Once the carious cavity has been formed,there is no way for dental hard tissue to regenerate.And the current therapy of carious cavity is only to remove caries tissue away by mechanical or chemical methods of cavity preparation.Besides,in order to get a better shape of the cavity,some healthy tissue need to be prepared for cavity filling to a certain amount.This treatment will always lead to excessive loss of teeth and growing possibility of crown crakes.The current situation reminds us that preventing the formation of middle and deep caries and doing some early interference of teeth without caries cavity is an important task for oral health prevention,which also accords with the principle of minimally invasive dentistry(MID).Tooth remineralization is one of the most important treatment techniques for MID.Enamel remineralization is of great value for the clinical prevention and therapy of early decayed enamel,such as the white spot caries after orthodontic treatment.If we make use of the structure of hard tissue which has not yet been damaged on the enamel surface of demineralized enamel,the further biomimetic and remineralizing structure will play a crucial role in retaining the whole tooth.However,the existing remineralization method is difficult to operate,and it is difficult to meet the basic needs of clinical operation for simple and quick operation and specific bonding on enamel surface.Also,the results are far from the natural enamel characterization.In the process of tooth development,amelogenin plays a vital role in the formation of enamel.It has the ability to induce amorphous calcium phosphate particles to be arranged in a directional order along the C-axis and to promote the transformation of amorphous calcium phosphate into hydroxyapatite after degradation.It was proved that in the rats' models which lack the key sequence of the amelogenin,enamel imperfecta was obvious in the naked eye.In this study,an innovative chimeric peptide sequence was synthesized mainly from the key sequence of the enamel protein and the specific hydroxyapatite bounding sequence.The aim is to provide a remineralization method for rapid biomimetic remineralization of dental enamel caries,which is guided by synthetic peptides.The in vitro dental experiments confirm the ability of synthetic peptides to induce amorphous calcium phosphate particles and remineralization on tooth surfaces.Then it will provide a certain basis for the remineralization of the clinical enamel.Methods:Carboxymethyl Chitosan(CMC)/ Acouphous Calcium Phosphate(ACP)nano-complexes solution was firstly synthesized through the addition of the CMC,calcium chloride and dipotassium phosphate into distilled water successively.ACP nanoparticles were degraded by 1% sodium hypochlorite(Na Cl O)from CMC/ACP nanocomplexes.The morphology of particles in different periods were tested by transmission electron microscope(TEM).The chimeric peptides were added to guide the arrangement of ACP nanoparticles and to bond ACP nanoparticles to the demineralized enamel surface specifically.X-ray diffraction(XRD),Scanning Electron Microscope(SEM),Confocal Laser Scanning Microscopy(CLSM),Nano-indentation tests were applied to check the remineralization effects.Results:1.CMC/ACP nano-complexes were obtained and could be kept without precipitation for a long time.2.After the degradation of Na Cl O and the guidance of chimeric peptides,ACP nanoparticles were arranged into oriented arrays before transforming into crystals and the enamel-like crystals were binded onto the demineralized surface tightly with the guidence of chimeric peptide.The newly formed enamel-like crystals were nearly well-organized and equipped with strong mechanical properties through the tests of SEM/TEM/XRD/CLSM3.According to the results from the Nano-indentation tests,it is surprising to find out that the remineralization group was equipped with the close mechanical properties(hardness/elastic modulus)to the natural enamel.Conclusions:The chimeric peptide which possesses with guiding and binding motifs was proved to be effective in demineralized enamel remineralization.The newly formed HAP crystals were equipped with the similar structure and mechanical strength to the natural enamel HAP.The study provides a novel method of enamel remineralization,which is of great value in prevention practice of enamel decay like the chalk caries after orthodontic therapy.