الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A new type of composite resin restorative material was recently introduced into the dental material characterized by lower polymerization shrinkage than other types of composite resin which represents a great breakthrough to clinicians. Consequently, the present in vitro study was aimed at achieving three goals.
First part of the study was to determine the hardness of silorane based composite (Filtek p90) and methacrylate based compoite (Filtek Z250) .A total of 20 disc shaped specimens were prepared from both composites then divided into 2 groups again each group was subdivided into 2 sub group of 5 specimen each. The hardness was determined after storing the materials for 24h in distilled water as well as after ageing (thermocycling and storing for 4 weeks in water, or alcohol), using Vicker’s microhardness tester.
The second part of the study was to determine the flexural strength of the two composite materials. A total of 30 bar shaped specimens were prepared from both composites then divided into 2 groups again each group were sub divided into 3 sub group of 5 specimen each with the third group was kept as a reference. The flexural strength was determined after storing the materials for 24h in distilled water as well as after ageing (thermocycling and storing for 4 weeks in water, or alcohol), using universal testing machine.
The third part of the study was to measure and compare the surface roughness of the two composite materials. A total of 20 disc shaped specimens were prepared from both materials. The 20 disc shaped specimens were divided into 2 groups. Each group again was subdivided in to 2 subgroup of 5 specimens each, each subgroup undergone thermocycling in water (5000 cycle at 5/55°C), before storage in treatment solution. Prior and after thermo cycling and storage in treatment solution, the average values of surface roughness (Ra-μm) of all specimens were measured by means of Marsurf - PS1 profilometer.