Study On The Enhancement Of Zeolite A And Y On The Stability Of Resin-Dentin Bonding

Dental caries is a high-risk bacterial infectious disease that occurs in dental hard tissue.It is known as the three major non-communicable diseases that humans focus on prevention and treatment with cardiovascular and cerebrovascular diseases and tumors.It has become one of the focuses of global medical and health prevention and treatment.At present,direct bonding restoration of composite resin is the main treatment for caries.As the main structure in the treatment of caries,dentin is a natural biological tissue of inorganic-organic composite.In the process of bonding restoration,resin-dentin bonding interface will be formed between resin monomer and dentin collagen fiber.The stability and durability of this bonding interface determine the therapeutic effect of caries restoration.There are many factors that lead to interface instability during resin-dentin bonding,including:1)the acidic monomers in the bonding system activate endogenous enzymes while dissolving dentin minerals,resulting in the degradation of exposed collagen fibers in the bonding interface;2)Some resin monomers promote water enrichment at the bonding interface due to their hydrophilicity,which leads to resin hydrolysis;3)Saliva components,bacteria and by-product enzymes in the oral micro-environment can also cause further hydrolysis of collagen fibers and resins.In view of the above factors,how to reduce collagen fiber degradation,resin hydrolysis and bacterial adhesion is the key to improve the stability and durability of the bonding interface.Therefore,this paper designed and developed a zeolite addition system with comprehensive functions such as antibacterial,anti-endogenous enzyme and remineralization,which significantly enhanced the stability of dentin bonding and was expected to greatly improve the therapeutic effect of caries.Zeolite is a crystalline microporous aluminosilicate material,which can undergo continuous ion exchange and release in local body fluid environment.It has good biocompatibility,high thermal/chemical stability and acid resistance,and the Si-OH on its structural surface can be mutually soluble with the bonding system,which has good clinical application prospects.Among the 248 zeolite structures reported so far,zeolite A and zeolite Y zeolites are two kinds of zeolite materials that have been discovered earlier and studied more maturely.In this study,we used zeolite A and zeolite Y with different sizes as research carriers to load Ag⁺and Zn²⁺functional ions,and improved the one-step self-etching bonding system,in order to comprehensively improve the ability of resisting interface degradation such as antibacterial,anti-endogenous enzymes and promoting remineralization during dentin bonding to strengthen the stability and durability of dentin bonding.By selecting appropriate metal cations and zeolite structure types and modifying zeolite crystals,three zeolite addition systems that can significantly improve the long-term stability of resin-dentin bonding interface were developed in this paper.The main research results are as follows:In the second chapter,we first synthesized zeolites A with low Si/Al ratio and crystal size of 500 nm-1μm,AgAand ZnA zeolites with high loading were prepared by Ag⁺and Zn²⁺ion exchange.The basic characterization and biological characterization（biocompatibility and minimum inhibitory concentration）of zeolites were tested,and then the effects of zeolites on the physical and chemical properties,antibacterial properties and bonding properties of the modified bonding system were detected.The results showed that AgAand ZnA zeolites had good biocompatibility when the concentration is below 2 mg/m L.It showed good sustained release ability of Ag⁺and Zn²⁺in artificial saliva.The 0.2 wt.%AgAzeolite significantly improved the antibacterial properties of the bonding system without affecting the physical and chemical properties and bonding properties.The 0.2 wt.%ZnA zeolite could improve the wettability of dentin while endowing the bonding system with antibacterial properties.The application of 0.2 wt.%ZnA and AgA/ZnA（Ag:Zn=1:1）zeolites could increase the long-term dentin bonding strength by～25%under 5000 thermal cycles.The AgAand ZnA zeolites synthesized in this experiment rely on the ion sustained release effect to exert the interface antibacterial function and strengthen the interface stability,while the function of zeolite entering the water-bearing area of collagen fiber gap remains to be studied.In the third chapter,in order to further promote the zeolite to enter the interstitial space of collagen fibers and study its ability to inhibit endogenous enzymatic hydrolysis and promote remineralization in the interstitial space of 40 nm collagen fibers,we prepared ZnY zeolite with a crystal size of about 20 nm.The basic characterization of zeolites,biocompatibility characterization,and physicochemical properties,endogenous enzyme activity,remineralization ability,microleakage and bonding properties related to the modified bonding system were characterized.The results showed that ZnY zeolite had good biocompatibility when the concentration is below 10mg/m L.It showed good Zn²⁺sustained release ability in artificial saliva.The addition of 0.2 wt.%,0.5 wt.%and 1 wt.%ZnY zeolites could effectively improve the wettability of the bonding system to dentin,inhibit the activity of endogenous enzymes in the interface,and realized the mineralization of the interface under the condition of artificial saliva storage for 7 days.The precipitation promoted the remineralization of the bottom of the interface and the dentinal tubule wall,reduced the microleakage of the dentin bonding interface under the condition of artificial saliva aging for 3 months,and increased the long-term bonding strength of dentin aged by 5000 thermal cycles by～28%.In addition,1 wt.%ZnY zeolite also enhanced the crosslinking of collagen fibers.In this experiment,1 wt.%ZnY zeolite is densely distributed in the adhesive system,and its penetration between collagen fibers spaces needs to be strengthened.In the fourth chapter,in order to further improve the dispersion and penetration ability of zeolites,we used hexadecyltrimethoxysilane（HDTMS）to modify the surface of ZnY zeolite to prepare hydrophobic ZnY-HDTMS zeolite,and systematically characterized the effect of this zeolite on the durability of dentin bonding.The results showed that the hydrophobic ZnY-HDTMS zeolite could still maintain good Zn²⁺sustained release ability in artificial saliva and had good biocompatibility.The 0.2 wt.%,0.5 wt.%and 1 wt.%ZnY-HDTMS zeolites effectively inhibited the endogenous enzyme activity in the resin-dentin bonding interface,promoted the remineralization of the resin-dentin bonding interface and the dentinal tubule wall,and further realized the remineralization between collagen fibers and reduced the microleakage of the bonding interface.On the basis of this,the long-term bonding strength of dentin under 5000thermal cycles was significantly increased by～46%.Among them,0.5 wt.%and 1 wt.%ZnY-HDTMS zeolite could also effectively promote the crosslinking of collagen fibers,and had a broader application prospect in improving the stability of dentin bonding.The results of this study show that Ag⁺and Zn²⁺loaded zeolite A and zeolite Y can significantly enhance the long-term stability of the dentin bonding interface.The development of dentin bonding system based on zeolite inorganic functional materials can provide new ideas for improving the therapeutic effect of caries restoration.