Occlusion Of Dentinal Tubules By Hydroxyapatite Guided By Amyloid-like Protein

Objectives:Dentinal hypersensitivity is one of the common dental hard tissue diseases.When it attacks,patients can barely endure the sore teeth and range of attack can be limited or extensive.The current reported treatments have poor long-term efficacy and are prone to lead to recurrence.Therefore,it has become an urgent need to find a treatment method which is simple,quick,and long-term stable.In this study,polyethylene glycol(PEG)was grafted on lysozyme to get amyloid-like protein-PEGylated lysozyme(lyso-PEG),and the phase-transformed lyso-PEG solution was obtained after treating with a reducing agent TCEP.Phase-transformed lyso-PEG coating was constructed on the surface and deep regions of dentinal tubules.Relying on its surface active functional group,Phase-transformed lyso-PEG induced the production of hydroxyapatite to achieve the purpose of sealing dentinal tubules.Methods:1.First,PEG was grafted on lysozyme to obtain lyso-PEG,and the reducing agent tris(2-carbonylethyl)phosphoric acid hydrochloride(TCEP)was prepared.The phase-transformed lyso-PEG solution was obtained by mixing with equal volume of the above two solutions.Collect the intact teeth obstructed due to the preventive extraction of orthodontics without caries,flaws,cracks,abrasion or other defects.Prepare the dentinal hypersensitivity model samples which were divided into 3groups:dentinal hypersensitivity control group,phase-transformed lyso-PEG treatment group and Green Or ~TMM positive control group.Put the samples in dentinal hypersensitivity control group and phase-transformed lyso-PEG treatment group into artificial saliva for 7 days.2.The results of lysozyme grafted polyethylene glycol were detected by MALDI-TOF and whether or not phase-transformed lyso-PEG adhered to the surface and deep regions of dentinal tubules was observed by Confocal Laser Scanning Microscopy(CLSM).Field Emission Scanning Electron Microscope(FESEM),X-ray diffraction(XRD),Energy Dispersive X-ray detector(EDX)were applied to characterize dentinal tubule sealer's microstructure and surface morphology.3.Mouse fibroblasts(L929)were cultured in vitro and colonized on the surface of teeth samples modified by phase-transformed lyso-PEG and phase-transformed lysozyme,and their biocompatibility was evaluated by CCK-8 cell viability assay.The dentinal tubule occlusion of the phase-transformed lyso-PEG modified teeth samples was assessed in the rat animal experiment simulating the real oral environment.Results:1.The MALDI-TOF mass spectrum showed that polyethylene glycol was grafted on lysozyme.The results of CLSM showed that the phase-transformed lyso-PEG could adhere to the surface and deep regions of dentinal tubules and could penetrate into the tubules about 20?m.2.The FESEM results revealed that the phase-transformed lyso-PEG modified dentinal tubules were densely sealed,and the sealer precipitating within the tubules exceeded 20?m beneath the surface.However,Green Or~TMM could only locate on the dentin surface rather than the deep regions of dentinal tubules.XRD and EDX results suggested that the sealer induced by phase-transformed lyso-PEG was hydroxyapatite close to the inorganic component of natural dentin.3.The cell viability experiment confirmed that phase-transformed lyso-PEG has good biocompatibility.The animal experiment simulating the real oral environment showed that the phase-transformed lyso-PEG modified dentinal tubules were densely occluded and appeared remarkable antibacterial effect,the same as in vitro experiment.Conclusions:In this experiment,polyethylene glycol was grafted on lysozyme and the phase-transformed lyso-PEG was formed by phase transformation system.Phase-transformed lyso-PEG was applied as a surface modification material to stably adhere to the surface and deep of dentinal tubules,which could induce hydroxyapatite to occlude dentinal tubules.This process is mild,simple,rapid,economic and stable.In this regard,phase-transformed lyso-PEG should be considered as a new active layer for promoting mineralization in dentinal tubules.Amyloid-inspired surface modification can become a promising next-generation clinical strategy for treating dentinal hypersensitivity.