The Effects Of Pamam Dendrimer On Matrix Metalloprotenaseas And Remineralization In Human Dentine

At present the main method is to use a resin adhesive restorative repairing the defect of dentin in clinical.However,due to the characteristics of dentin structure and the complex oral environment,the long-term effects of the resin–dentin bonds are facing great challenges in clinical practice.There are two main factors that affect the longer durability of adhesive restorations.Firstly,resin monomer is difficult to completely infiltrate into the demineralized dentin collagen fibrils during the bonding process leaving a weak marginal leakage between the collagen fibrils and resin monomer at the bottom of hybrid layer.In addition,the matrix metalloproteinases(MMPs)in the exposed collagen fibrils would be activated by the acidic environment and degrade the resin-dentin interface over time.Presently,different bonding strategies were reported to improve the long-term adhesion of dentin by the means of inhibition dentin MMPs and enhanced dentin mechanical properties.But there were few studies reports on combined effects of those strategies and the clinical effects were uncertain.This research have investigated the effects of carboxyl-terminated PAMAM dendrimers(PAMAM-COOH)on the problem of longer durability of adhesive restorations.Objective The objectives of this study were to incorporate CHX to G4.0 PAMAM-COOH,and investigate their combined effects of inhibiting soluble rhMMP-2 and endogenous MMPs activity and inducing remineralization on human dentine.Methods Chlorhexidine(CHX)and PAMAM-COOH were synthesized(CHX-PAMAM-COOH),evaluated their combining capacity by ultraviolet spectrophotometer and characterized by Fourier transform infrared spectroscopy.The experimental group were set as four group : CHXPAMAM-COOH group,PAMAM-COOH group,CHX group and control group(deionized water group).Firstly MMP Activity Assay Kit was used to detect the effects of different treatments on the activity of soluble rhMMP-2 and dentin endogenous matrix metalloproteinases respectively.In order to evaluate the effect of different treatments on the activity of dentin collagenase,the loss of dry mass after 30 days were measure.What's more,the activity of matrix metalloproteinases in dentin treated with different experimental groups was qualitatively studied by in situ zymography analysis.Finally samples were pretreated with different experimental groups and then incubated in artificial saliva.After 7 and 14 days,the remineralization in dentin surfaces were examined using a field emissionscanning electron microscope.SPSS(versions 24.0)software was used for statistical analysis of the data.Results(1)Ultraviolet spectrophotometer test results show that different concentrations of CHX could be combined with PAMAM-COOH,and the 2%CHX combined with PAMAM-COOH the most.The characteristic peaks of CHX appeared on the surface of PAMAM-COOH chemical groups from FTIR results,meaning that CHX seemed to adsorb to the surface of PAMAM-COOH dendrimer.(2)The results of PAMAM dendrimer on rhMMP-2 showed that the activity treated with PAMAMCOOH was increased.And the rhMMP-2 activity were significant reductions in the CHX-PAMAM-COOH and CHX groups.But there was no significant difference between them after 1h reaction(P>0.05).(3)The results of endogenous MMPs activity assay showed that dentin endogenous MMPs activity in PAMAM-COOH group had no significant change(P>0.05).Compared with control group,the total MMPs activity in CHXPAMAM-COOH group and CHX group were decreased(P<0.001).And in the time of 30 min the effect of CHX-PAMAM-COOH on inhibiting the endogenous MMPs in dentin was better than that of CHX group(P<0.001).(4)The loss of dry mass in four group were all decreased.Compared with control group the loss of dry mass in CHX-PAMAM-COOH group and CHX group were reduced significantly.And the loss of dry mass in CHXPAMAM-COOH group was lower than that of CHX group(P<0.05).(5)The situ zymography analysis showed same result as dentin endogenous MMPs activity assay that dentin samples pretreated with CHX-PAMAMCOOH exhibited almost no fluorescence signal after 48 h incubation indicating effective inhibition of dentine collagenase.(6)After 2 weeks incubation in artificial saliva,SEM showed distinct rod-like crystals minerals on the surface of dentin sample pretreated with PAMAM-COOH and CHX-PAMAM-COOH and the remineralization effect was stronger than that in CHX group.Conclusion CHX-PAMAM-COOH can perform a dual function on the dentin surface.It was proved to effectively inhibit rhMMP-2 and endogenous MMPs and could introduce remineralization in demineralized dentin,which has great potential as novel material to enhance durability of adhesion.