الفهرس 
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Abstract
One of the most important shortcoming of dental composites is their degradation as dental composite may either exposed intermittently or continuously to chemical agents found in saliva, food and beverage. So, pH has been shown to have an effect on the degradation of dental composite as it varies in oral environment. Degradation of dental composite occurs as a result of incomplete polymerization and influence of oral fluids.
This study was aimed to study the degree of conversion and effect of different pH solutions on properties of recently introduced composite restorative materials including solubility, hardness, wear and diametral tensile strength. The present study was carried out using restoraive materials with different monomer and filler systems such as ormocer–based restorative material (Admira) and a nanofillled composite (Filtek supreme XT).
Depending on the results and within limitations of this study, we can conclude the followings:
1. Degree of conversion of filtek supreme XT are higher than that of ormocer restorative material.
2. The lower the pH, the higher the solubility, the lower the hardness, the higher the wear and the lower the diametral tensile strength of the tested materials.
3. There was no significant difference between pH5 and pH 7 from distilled water (control group) for hardness and diametral tensile strength values of both tested materials.
4. The hardness and diametral tensile strength of filtek supreme XT are higher than that of ormocer restorative material in different storage media.
5. The wear values for nanofilled restorative material were less than that of ormocer restorative material in different storage media.