الفهرس 
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Abstract
This study was attempting to assess the use of ceramic filler in reinforcement of heat cured acrylic resin as a denture material using silanized and non silanized ceramic fillers.
This in-vitro study was performed on thirty identical maxillary upper dentures made from heat cured acrylic resin, ten of them reinforced with zirconia oxide powder, another ten of them reinforced with zirconia oxide powder treated with silane coupling agent.complete dentures were divided into three groups :
-Group (A): Ten maxillary dentures were constructed of heat-curing acrylic resin denture base material resin, conventional processing took place by flasking the waxed up denture and processing in heat cured acrylic denture base material following the compression molding techniques, water baths at 74 c for 90 min. followed by 30 min. boiling were used, no finishing and polishing were done, only excess material were removed, this group was used as a control group.
-Group (B): Ten maxillary dentures were constructed of heat-curing acrylic resin denture base material which was resin reinforced with 15% by weight of zirconia ceramic powder without treatment with silane coupling agent, Weighting of ZrO2 powder was done using an electronic balance . Thorough mixing of zirconia oxide powder with the polymer was done using porcelain mortar and pestle, then the mixture was passed through a sieve to produce more homogenous mix, and the monomer was added to the mixture, conventional processing then was done as mentioned before.
-Group (C): Ten maxillary dentures of heat-curing acrylic resin reinforced with 15% by weight zirconia powder after its treatment with silane coupling agent. A solution of 0.3 g of silane coupling agent in 100 ml of acetone was used to treat 30 g of zirconia powder (ZrO2). The oxide powder was stirred in the coupling agent/acetone solution with a magnetic stirrer, for 60 minutes , after which acetone was completely evaporated using a rotary evaporator. Weighting of ZrO2 powder was done using an electronic balance. ZrO2 powder was added in a concentration of 15% by weight acrylic polymer. Thorough mixing of the oxide powder with the acrylic polymer powder was carried out using porcelain mortar and pestle, then the monomer was added to the mixture, then processed as mentioned before.After processing, resin maxillary dentures designed for strength testing were stored in deionized water at room temperature for two weeks before testing A load applicator in the form of two arms connected by a T-Shaped bar was cast in cobalt –chrome alloy. The terminal end of each arm was made to fit the occlusal surface of the second premolar and first molar on each side.The load applicator was mounted to the upper jaw of a universal testing machine. The modified acrylic cast with the denture was fixed to the lower metallic plate of the testing machine. A vertical load was applied at a crosshead speed of 0.5mm/min until denture fracture as indicated by the break detector of the testing machine. The load deformation curve for tested denture was plotted by means of data analysis software installed in a PC connected to the testing machine.
Maximum load recorded at denture fracture (LF)in Newton(N)was recorded.
Sample of each group was examined by Scanning electron microscopy shown in after testing. All data were collected and statistically analyzed using stats Direct software version 2.5.7
Results showed that reinforcement of heat cure denture base material with silanized zerconia fillers (group C) increased the fracture resistance significantly compared to the other studied groups. It was evident that the amount of load needed to fracture dentures made of heat cured acrylic resin reinforced with non silanized zirconia (group B), was significantly higher than that load needed to fracture dentures made of conventional heat cured acrylic resin.