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Influence of BisGMA concentration and photoinitiator on the degree of conversion and flexural strength of the adhesive monomers cured by LED device


The conversion degree of adhesive monomers facing phases separation, due to the amount of water emerging from dentin surface after acid conditioning, is still an important factor for the maintenance of stability of adhesive interface. This study aims to determine BISGMA concentration required for an efficient curing of aqueous and resin phases (step1), to determine the quantity and quality of the photoinitiator system (step 2), and also to determine the strength flexural of the adhesives models (step 3). The 1st phase will involve the manipulation of adhesive models with different concentrations of BisGMA / HEMA in the presence of water and groups of 2, 3, 4, and 5 photoinitiators: 2 (CQ e EDMAB); 3- (CQ, DMAEMA, DPIHP); 4- (CQ, DMAEMA, DPIHP e QTX 10% ); 5- (CQ, EDMAB, DMAEMA, DPIHP e QTX 10 ou 5%). In phase 2 adhesives models containing 55% BISGMA and 45% HEMA weight ratio will be manipulated and the same associations of photoinitiators will be incorporated into the mixture. After mixing and agitating for 24 hours water will be incorporated into the mixture to induce adhesive phases separation (1 minute agitation and 60 minutes centrifuging). Aqueous and resin phases, and also pure resin will be assessed by FTIR (Fourier Transformed infra red spectroscopy). A drop of the liquid to be analyzed will be deposited on the ATR crystal surface to collect spectra, allowing to monitor the degree of conversion during and after polymerization using a LED with 1100mW/cm2 of intensity (20min of measurement). Data will be registered in excel format and transferred to Origin 6.0 software for obtaining graphs and respective conversion degree of monomers. Specimens (n-100) from the different adhesives with the same composition of phase 2 will be fabricated from metal matrix (15x2x2mm). Specimens will be submitted to flexural testing in a universal testing machine - EMIC, using 10Kg cell load and 0.5mm/min crosshead speed under two periods of evaluation (immediate and 6 months of storage in artificial saliva). If normality is obtained, the most appropriate statistical model will be performed. (AU)

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