Study On In Situ Remineralization Of Mixed Layer Induced By DR-PAM To Improve The Bonding Durability Of Dentin

Objecctive:The purpose of this subject is to solve the problem of collagen degradation in the biomimetic remineralization process.Based on the good remineralization ability of PAMAM-NH₂,the amino acid sequences-DSp ESp Sp EEDR-with specific collagen-binding ability are introduced into the easily modified functional groups on the surface of PAMAM.It is expected that it can be endowed with the abilities of cross-linking and stabilizing collagen while preserving PAMAM’s remineralization and antibacterial properties.The aim of this study is to evaluate the collagen binding,biomimetic remineralization,and antibacterial properties of DSp ESp Sp EEDR-NH-PAMAM（DR-PAM）as a dentin bonding pretreatment agent,and to provide a new idea or technique for improving the durability of dentin bonding.Methods:Based on the fifth generation PAMAM-NH₂,amino acid sequences-DSp ESp Sp EEDR-with specific collagen-binding effect were introduced on its surface to synthesize DR-PAM complex.Its molecular structure was verified by nuclear magnetic hydrogen resonance（¹H NMR）and fourier transform infrared spectroscopy（FTIR）.The optimal experimental concentration was selected by cytotoxicity test,and the immediate bonding strength of resin-dentin as pretreatment agent was tested by micro tensile test.Then the binding ability to collagen fiber was detected by the hydroxyproline release（HYP）,fluorescence staining of isothiocyanate（FITC）and circular dichroism analysis（CD）.Next,the scanning electron microscopy（SEM）and elemental analysis（EDS）,X-ray diffraction（XRD）,infrared spectroscopy（FTIR）,transmission electron microscopy（TEM）and selective electron diffraction（SAED）were used to investigate its ability to achieve biomimetic remineralization of dentin.Finally,the inhibition effect on S.mutans and E.faecalis was verified by dead/alive staining.Result:In this project,DR And DR-PAM were successfully synthesized.CCK-8study showed that DR-PAM had good biocompatibility and the experimental concentration was determined to be 1 mg/m L.The micro tensile experiment proved that DR-PAM would not affect the immediate bonding strength of dentin.The results of HYP,FITC and CD showed that DR and DR-PAM had strong binding force with collagen fibers,which enhanced the ability of anti-enzymatic hydrolysis.The remineralization experiment proved that DR-PAM could induce the bionic remineralization of collagen fibers,and the results of dead/alive staining showed that the modified DR-PAM still had certain antibacterial effect.Conclusion:The DR-PAM synthesized in this study had good biocompatibility and did not affect the immediate bonding strength of dentin.At the same time,it could firmly combine with collagen fibers and improve the stability and enzymatic hydrolysis resistance of demineralized dentin collagen.Moreover,the collagen protective effect of PAMAM-NH₂ was successfully endowed without affecting the remineralization and antibacterial effect of it.It had potential value in improving the durability of resin-dentin bonding.