Construction Of IP6-PAMAM-GL13K Extrafibrillar Deminerlization System And Its Application In Dentin Bonding

Objective:Stomatologists at home and abroad have brainstormed and worked together to solve the problem of poor durability of resin-dentin bonding caused by the existing dentin bonding system.The proposed technology of"extrafibrillar demineralization"has contributed new ideas and methods to solve this issue.The purpose of this study is to graft small molecule powerful chelating agent phytic acid（IP6）and antimicrobial peptide（GL13K）on the surface of polyamide-amine dendrimers（PAMAM-NH₂）to construct the IP6-PMAAM-GL13K system.The ability of the complex to achieve extrafibrillar demineralization and antibacterial as a pretreatment agent for dentin bonding was tested,and to evaluate its effect on the durability of resin-dentin bonding.Methods:（1）The IP6 and GL13K were introduced into the fifth-generation dendrimer PAMAM-NH₂by chemosynthetic methods.The IP6-PAMAM-GL13K system was detected and characterized by fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance（NMR）,gel permeation chromatography（GPC）and high performance liquid chromatography（HPLC）.（2）To evaluate the ability of IP6-PAMAM-GL13K solution as a pretreatment agent to achieve selective demineralization and the effect on dentine bonding strength.Scanning electron microscope（SEM）observed the microscopic morphology of collagen matrix formed by IP6-PAMAM-GL13K on the surface of dentin.Atomic force microscope（AFM）observed the surface topography of the control group and the experimental group.Gelatinolytic activity within the hybrid layer was examined using in situ zymography.Three common caries pathogenic bacteria were selected to detect the inhibitory effect of the system on the adhesion interface of dentin.Finally,the toxicity of IP6-PAMAM-GL13K solution on human dental pulp cells and fibroblast was evaluated by CCK-8.Results:（1）FTIR and NMR confirmed that the IP6-PAMAM-GL13K complex was successfully constructed.The molecular weight of the polymer met the requirements of demineralization outside the fiber,and its purity was>95%,which met the experimental requirements.（2）The bond strength test showed that IP6-PAMAM-GL13K solution could achieve the same effect as 37%phosphoric acid etching on the dentin surface,and there was no statistical difference between the bond strength of"wet bonding"and"dry bonding"（P>0.05）.SEM results showed that the demineralized collagen fibers on the dentin surface treated with IP6-PAMAM-GL13K solution did not shrink and deform,and AFM showed that the roughness of the dentin surface after treatment with IP6-PAMAM-GL13K solution was significantly greater than that of the control group.Hybrid layers conditioned with IP6-PAMAM-GL13K showed significant decrease in gelatin activity as compared with the control group（P<0.05）.Antibacterial testing indicated that IP6-PAMAM-GL13K significantly inhibited bacteria grown on the dentin discs as compared with the control group（P<0.05）.CCK-8 assay showed that IP6-PAMAM-GL13K complex had good biocompatibility.Conclusions:The new dentin bonding pretreatment agent IP6-PAMAM-GL13K synthesized in this project has good biocompatibility and selective collagen fiber demineralization ability,which can achieve strong bond strength,have antibacterial properties and inhibit matrix metalloproteinases,effectively avoiding the problem of insufficient durability of resin bonding.This has a good clinical development prospect in extending the service life of resin restorations.