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Multi-user equipment approved in grant 2022/02823-3: Fourier transformed infra-red spectrometer

Abstract

In previous studies with research groups from the Universities of Birmingham and Manchester, we obtained important results related to the significant increase in the rate of polymerization and mechanical properties of experimental resins. Nevertheless, the changes in the photoinitiator systems should also contemplate a better biocompatibility of the materials to the buccal tissues. With this, new co-initiators of polymerization for systems using camphorquinone as a sensitizer were developed. These new agents have demonstrated similar efficiency to the commonly used co-initiators regarding monomeric conversion. However, there is no studies about the influence of the new compounds on the chemical-physical properties of the dental resins or data about the compatibility of these agents to the human dental pulp cells (hDPCs). Therefore, this study aims to evaluate the influence of new co-initiators of polymerization on experimental resin systems' chemical-physical and biological properties. On Part 1, hDPCs will be isolated from the dental pulp of sound human third molars. The co-initiators SE06, SE09, SE19, SE20, combined with the widely used dimethylamino ethyl methacrylate (DMAEMA) and ethyl 4-dimethylamino benzoate (EDA) will be diluted in dimethyl sulfoxide (DMSO), obtaining different concentrations (0,5mM, 1mM, 2mM, 4mM). Control groups will be established (culture medium and maximum concentration of DMSO). hDPCs 10 x 104 cells/well) were seeded in 96 well plates and incubated at 37o C and 5% CO2. The cells were exposed to different concentrations of co-initiators and maintained in a culture medium for 24 h. After this, the culture medium with the monomers will be removed and analyzed about the release of inflammatory cytokines (IL-1b, IL6, IL-8, IL-10, TNF-±). The cells will be collected, the DNA extracted, treated with Mspl and Hpall enzymes to evaluate the global epigenetic regulation pattern (LINE-1, DNMTs e TETs) and the specific genes (inflammatory cytokines) for real-time PCR. The mitochondrial metabolism (MTT) and the cell death (flow cytometry) will be also evaluated. In Part 2, experimental composites with the co-initiators SE06, SE09, SE19 e SE20)combined to camphorquinone (0.5%) and diphenyliodonium hexafluorophosphate (0.5% DPI) will be evaluated. The resins will be prepared varying the ration initiator/co-initiators (1:1 and 1:2). The mitochondrial metabolism of hDPCs, cell death, cytokine release, and epigenetic regulation of the genes will be analyzed. The degree of conversion of the resin systems will also be evaluated by Fourier transformed infrared (FTIR). At Part 3, a monomeric base containing bisphenol A diglycidyl methacrylate (BisGMA) 50% and triethylenoglycol dimethacrylate (TEGDMA) 50% will be prepared, with 0.5% of CQ and 0.5% DPI. The groups will be established according to the co-initiator (SE06, SE09, SE19 e SE20, DMAEMA and EDAB, used as control) and the concentration of the compounds (1 and 2%) used, obtaining 12 groups. The resins will be added 60% wt of filler particles (BA-Al-Si). After the preparation of the composites, the degree of conversion will be evaluated in real-time on the FTIR. The water sorption and solubility will be also analyzed. The flexural strength and modulus will be obtained by the three point bending test. The bonded disc technique will evaluate the composites' volumetric shrinkage, and the shrinkage stress will be evaluated on the Universal Testing Machine. For all parts of the study, the homogeneity and normality of the data will be analyzed, and then the appropriated statistical test will be applied (parametric or non-parametric). The significant level used will be 5%. (AU)

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