Effect And Mechanism Of Cross-scale Reinforcement On Micro-Interface And Macro-mechanical Properties Of Dental PBO Fiber-Reinforced Resin Matrix Composites

BackgroundThe comprehensive properties of the commonly used fiber posts are limited by the fiber reinforcements with lower strength(glass fibers or quartz fibers).By introducing the fiber reinforcements with higher performance,it is possible to improve the comprehensive properties of fiber-reinforced resin-based composites(FRMMC)used as dental post materials.Poly-p-phenylene benzobisoxazole(PBO)with high strength and high modulus was introduced into this field successfully in our preliminary study,and we found that the PBO-FRMMC was superior in fatigue resistance than quartz fiber-FRMMC.However,the performance of its interface was still not ideal,while the PBO-FRMMC had not yet achieved the expected performance.Therefore,the improvement of the interface performance is the key point that must be resolved before introducing high-performance PBO fibers into the dental field.Based on the existing advantages,how to further optimize the performance of PBO-FRMMC through interface modification is the focus of current research.ObjectiveInspired by the theory of "cross-scale reinforcement",a new interface model is proposed in our study.By introducing the "cross-scale reinforcement" based on modified PBO fibers with nano-sized zinc oxide and cage silsesquioxane(POSS),we propose to modify both the reinforcing fiber and the Bis-GMA matrix simultaneously,further optimize the interface binding and improve macro mechanical properties of composite materials.Through different observation methods,we will conduct in-depth research on the interface regulation mechanism and explore the influence of different interface states on the mechanical properties of composite materials,in order to further enrich the interface regulation theory and provide new ideas and theoretical basis for the improvement of FRMMC in the field of dental post materials.Materials and methodsIn the first two chapters of the experiment,the pretreatment process of grafting nano ZnO on the surface of PBO and the appropriate doping ratio of ZnO NPs in Bis-GMA resin matrix were optimized.In Chapter 3,we introduced the "PBO-nano ZnO-POSS" cross-scale reinforcement structure into the single fiber-resin interface and established a monofilament mechanical model.At the same time,though comparing the modification effect of different modified PBO fibers on the interface,we optimized the best improved interface,and further explored the regulation mechanism.In Chapter 4,we compared and analyzed the effects of different cross-scale reinforcement structures on the flexural properties of PBO fiber-reinforced resin-based composites,and explored the relationship between micro-interface bonding and macro-mechanical properties.In Chapter 5,we performed a preliminary evaluation of the in vitro cytotoxicity of the selected FRMMC reiforced with "PBO-nano ZnO-POSS" cross-scale structure.Results1.Oxidation pretreatment was more suitable for grafting ZnO NPs,and carboxylation pretreatment was more suitable for grafting ZnO NWs.2.The Bis-GMA resin matrix with ZnO NPs(1.0 wt%)had the highest flexural strength(120.05±10.69 MPa).3.The cross-scale reinforcement with "PBO-ZnO NWs-POSS" showed the best effect on the improvement of the interface between monofilament PBO fibers and resin,with the form of transverse crystals at the interface.The mechanism of the modification might be the result of multiple factors,including mechanical locking,chemical bonds,hydrogen bonds,and intermolecular forces.4.The FRMMC obtained by compounding the cross-scale reinforcement(PBO-ZnO NWs-POSS)and Bis-GMA-(1.0 wt%ZnO NPs)showed the highest flexural strength under static load(1334.59±44.94MPa),and the flexural modulus was equivalent to human dentin.5.The cross-scale reinforced structure with better micro interface combination had better macro performance.6.There was a synergistic interaction between the fiber surface modification treatments and the nano-modified resin treatments.7.The preferred cross-scale enhanced PBO-FRMMC had no obvious cytotoxicity to the human gingival fibroblasts,and the cytotoxicity grade was 0 grade in vitro.ConclusionBy constructing a cross-scale reinforcement structure,both the interface integration and the flexural properties of FRMMC were successfully improved.Thus,a potential dental composite material was obtained.