Mechanical and environmental properties of denture base poly (methyl methacrylate) filled by barium Titanate
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Date
2006
Authors
Elshereksi, Nidal Wanis
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Abstract
The aim of the present study is to investigate the utilization of barium titanate (BaTiO3) as a radiopacifier in poly (methyl methacrylate) (PMMA) for dental base material in order to obtain a radiopaque polymer. The formulation used in this study comprises of PMMA, BaTiO3, benzoyl peroxide (BPO) as the initiator, methyl methacrylate as the monomer and ethylene glycol dimethyl acrylate (EGDMA) as the cross-linking agent. The BaTiO3 was treated by a silane coupling agent, 3-trimethoxysilylpropyl methacrylate (γ-MPS), prior to its incorporation into the solid components (PMMA, BPO). The surface treatment was demonstrated using energy-dispersive X-ray (EDX). The specimens were prepared by adding powder to the MMA monomer followed by hand mixing as is standard dental laboratory practice. Four percentages of the filler were mixed with the polymer powder phase to prepare the 4 polymer composite samples i.e. 5, 10, 15, and 20 wt. Moulds were filled with the mixture at its dough stage and subjected to pressure at 14 MPa for 30 min at room temperature. The curing was carried out using a water bath at 78°C for 1.5 h. The samples were tested for tensile, flexural properties and fracture toughness. The results show that the incorporation of BaTiO3 filler into PMMA matrix resulted in an increase tensile and flexural modulus with slightly reduction in tensile and flexural strength while fracture toughness decreased. Increases in the amount of BaTiO3 incorporated to PMMA matrix, increases the brittleness of the resulting composites. The morphology of the specimens was examined using electron scanning microscopy (SEM). The influences of filler content on the surface hardness were also studied. The results showed an improvement on surface hardness of PMMA composite. The thermal properties of PMMA composite were evaluated using differential scanning calorimetry (DSC), thermogravimatric analysis (TGA) and dynamic mechanical analysis (DMA). It was observed that the presence of treated filler did not cause any significant changes on the thermal properties of the composite. Studies on absorption and solubility in water and simulated body fluid (SBF) revealed that the filled samples showed lower solubility and absorption as compared to the unfilled samples. The effects of environmental condition on the surface hardness and the fracture toughness were also studied. The results disclosed a reduction on surface hardness of PMMA matrix and PMMA composite (10 wt%) by 15.5% and 12.6%, respectively, after 28 days of immersion. Moreover, decrease in fracture toughness values, after 28 days of immersion, was found by 5.1% and 3.5% for neat PMMA and PMMA composite, respectively. Beside this, the influence of re-drying on fracture toughness was also estimated. The results show that there was a slight decrease in fracture toughness after re-drying by 9.3% & 10.5% for the PMMA matrix and the PMMA composite, respectively. Because of the assumption that ions from the artificial saliva diffused into the composite, and then ions can leach into the surrounding medium, the leaching experiment was applied. Subsequently, the leached elements were reported. Finally, the radio-opacity of PMMA composite was enhanced when the filler percentages increased.
Description
Master
Keywords
Materials and Mineral Resources Engineering , Denture base poly , Barium Titanate