الفهرس 
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Abstract
The aim of this study was to evaluate some of the properties of the silorane-based restorative composite as compared to the conventional resin-based composite. These properties include polymerization shrinkage, water sorption and solubility, tensile strength, flexural strength and fracture toughness.
Two types of resin composite filling materials were used in this study; FiltekTM Silorane, (P90), which is a silorane restorative material and FiltekTM Z250, which is a micro-hybrid resin-based restorative material.
For the measurement of polymerization shrinkage strains for both restorative materials, the specimen were packed into a stiff, white rectangular Teflon mold over a strain gauge foil and the light cured. Polymerization shrinkage strains were monitored during light curing for 40 seconds and for another five minutes post curing.
For the measurement of water sorption and solubility, disc specimens were prepared for each material, according to the ADA specifications No 27. for resin-based filling materials, using a Teflon mold. After curing, the specimens were stored in a freshly dried silica gel dessicator for an incubation period of 7 days. M1, m2, and m3 were obtained and water sorption and solubility were calculated in micrograms per cubic millimeter.
Tensile strength was measured using diametral compression test for tension according to the method described in the ADA specification No. 27 for resin-based filling materials. Disc specimens were prepared for each resin using a Teflon mold. Specimens were compressed diametrically in a Universal Testing Machine at cross head speed 1 mm/sec until fracture. The mean tensile strength of the sample was calculated in MPa.
Flexural strength was measured using three-point bending test according to the method described in the ADA specification No. 27 for resin-based filling materials. Beam specimens were fabricated for each resin in a stainless steel split mould. Each of the prepared specimens was subjected to three-point loading testing using the universal testing machine. The load was applied in the middle of the specimen at a cross head speed of 0.5 mm/min. The distance between the supports was 20 mm. Each specimen was loaded up to failure. The flexural strength (σ) was calculated in MPa.
For testing fracture toughness, specimens were prepared using the single -edge notched design. The notch was directed downward and the load was applied in the middle of the specimen at a cross head speed of 0.5 mm/min. The distance between the supports was 20 mm. Each specimen was loaded up to failure in a three-point bending test using the Universal Testing Machine. The fracture toughness was calculated in MPa.m1/2.
Results of monitoring polymerization shrinkage strains showed that Filtek Z250 undergoes higher polymerization shrinkage compared to that of Filtek silorane (P90). Also Filtek Z250 showed higher polymerization rates compared to that of Filtek silorane (P90).
Results have shown that the values of water sorption and solubility of Filtek Z250 was significantly higher than that of Filtek silorane (P90).
On comparing the strength properties, including tensile and flexural strengths, for both types of restorative materials, it was found that Filtek Z250 showed significantly higher values of tensile and flexural strength.
Regarding fracture toughness, Filtek silorane (P90) showed a significantly higher fracture toughness values compared to that of Filtek Z250.