| BackgroundThe ideal materials for dental post must have good aesthetic and biocompatible properties, meanwhile, excellent mechanical properties are also essential. The elastic modulus of metal or ceramic post is far higher than that of dentine, which is easy to cause the root fracture; while for FRC post, with a lower elastic modulus similar with dentine, could reduce the risk of root facture effectively. Although the existing FRC posts present many advantages, they have shortcomings as well. For instance, they can cause the post fracture easily as their flexural strength are much lower than metal post. Both the root fracture and the post facture are two common reasons leading to the clinical failure. Therefore, ideal materials for dental post must satisfy multiple requirements as following, such as aesthetic performance, biocompatibility, suiTab. elastic modulus matched to dentine and higher flexural strength. Thus, the improvement of the flexural properties for dental FRC post is urgently required.A novel FRC material for dental post with higher flexural properties can be obtained by introducing high performance fibers. However, the reinforcing fibers used so far for marketed dental posts are ordinary fibers, including carbon fiber, glass fiber and quartz fiber, which limite the performance of composite material.PBO fiber is known as the super fiber in21st century, which has been widely used in aerospace, defense and industrial areas for its excellent comprehensive performance. However, it hasn’t been used in dental biomaterials.ObjectivesThis study was aimed to develop a new FRC material using as dental materials by mixing the PBO fibers and epoxy resin. Besides, the mechanical properties were explained synthetically through the micro structures and mechanism on micro interfacial mechanical behavior. What’s more, the biocompatibility and flexural properties were investigated. All the above were studied to demonstrate the feasibility of introducing PBO fiber in the area of dental biomaterials.Materials and methodsPartⅠE-51was chosen as resin matrix, while MeTHPA as curing agent with two kinds of cure accelerators. The curing process was studied by means of Gel Time Testing and DSC. What’s more, a better resin system was determined through the study of mechanical and optical properties of resin castings.PartⅡPBO fibers after different surface modifications were analyzed by SFTS, SEM, IR, XPS, TG and IFSS, aiming at filtering the best method, with improved interfacial activity and interface bonding strength.PartⅢThe composite material was first prepared by using the resin (selected in experiment one) as matrix, and PBO fiber (selected in experiment two) as reinforcement, then tested for flexural properties. The relationship between micro interfacial bonding strength and macro-performance was evaluated.Part IVBiocompatibility of the composites was analyzed by cytotoxicity test according to GB/T16886.12-2005. All datas were analyzed with SPSS13.0. Levene’s test of homogeneity of variance was used (a=0.05).Results1. There was no statistical difference in the flexural strength and elastic modulus between the two groups with two different cure accelerators (P>0.05). However, the group using DMP-30as the cure accelerators presented a lower cure temperature, simple production process and lightly yellowed, Which was better than the group with2,4-EMI.2. SFTS:There was no difference in the SFTS of PBO fiber (P>0.05) among groups with different surface treatments.3. IR:There was no significant difference of IR between the groups before and after pretreatment. A strong absorption peaks appeared in the range of3400～3500cm-1after the plasma treatment. Besides, the peaks at2846.50cm-1,1404.98cm-1and1105.52cm-1were more prominent in the groups treating by the combination of plasma and coupling agent, compared with the control group. While these peaks turned weaker in the group with one simple treatment.4. TG:The results showed that the decomposition temperatures were606℃of pretreatment group, and622℃of groups after plasma treatment, respectively. While no significant change was observed after single Z-6040treatment.5. IFSS:There were significant differences among groups with different surface treatments(P<0.05). g test showed that, group E (11.19±0.59MPa) was significantly higher than other groups (P<0.05), followed by group F (9.01±0.56MPa), while there was no difference (P<0.05) among other four groups.6. SEM:The micromorphology of PBO fiber had significant differences among groups with different surface treatments. Compared to the smooth surface of the control group, there was an increasement in the surface roughness after surface treatment.7. The elastic modulus mean values of the composite materials after different surface treatments were no significant difference. While population mean values of flexural strength were statistically different. The results of q test between groups in flexural strength showed:the mean value of flexural strength in the plasma and coupling agent treatments group was531.636±34.880MPa, when in the coupling agent and plasma treatments group was531.678±47.145MPa. There was no significant difference in flexural strength values between the two groups, while the flexural strength values of the two groups were statistically higher than the others. There was no significant difference between the other four groups.8. In vitro cytotoxicity test showed that the cytotoxicity of the composite was grade1. The PBO fiber reinforced composite had no cytotoxicity.Conclusion1. The morphology and chemical composition of fiber surface varied differently according to different surface treatment methods, which were closely related to the modifying effects. The optimal modification technology for PBO fiber was determined as following:pretreatment with acetone first, then by means of coupling agent, finally by plasma treatment.2. Better performances could be provided along with better interface at the micro level. The flexural strength of composite materials was improved by modifications of PBO fiber, which was sufficiently to meet the requirement of root post in clinic (>400MPa). Besides, the elastic modulus was appropriate.3. In vitro experiments revealed that the cytotoxicity level of the composites was grade1, which was within the accepTab. range. Before coming into service, further animal and clinical trials need to be done.4. The study showed that it has certain feasibility to introduce PBO fiber into dental material, while the relevant theories and technics remained further exploration and perfection. The improvement of the interface combination between PBO fiber and resin matrix was not so obviously through SEM. However, it has great potential to improve the performance of composites, considering the limitation of fabricating processes and modification methods in the laboratory. |
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