الفهرس 
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Abstract
Surface roughness of restorative materials is a very complex phenomenon that is affected by several extrinsic and intrinsic factors. Roughness of restorative materials in the oral environment results from direct contact between tooth and the restoration during mastication, oral parafunctions, as well as toothbrushing .
The purpose of this study was to evaluate and compare the surface roughness of two resin composite restoratives under simulated tooth brushing machine with different brushing cycles and different types of tooth bristles.
A total of 120 specimens of two different types of light curing resin composite restoratives; (Methacrylate composite,ALPHA-DENT® and Silorane based composite Filtik P90 ) were made for this study. The specimens were made in the form of cylindrical disks, A mylar strip and a glass slide was placed over the resin composite. The specimens were light cured with light curing unit at 400-500 mw/cm2 , a major group of 60 specimens of each material were randomly divided into two minor subgroups (30 specimens) in each group according to the type of toothbrush bristle used in the study: (soft bristle & Medium bristle). Then these subgroups were devided again to three smaller subgroups according to the time of brushing, (10 specimens) (5 min, 10min, 15min).
Every specimen was measured for the detection of the average pre-brushing surface roughness (Ra1) and the results are represented in the tables(3 ). The specimens then brushed by soft or medium brush according to their group for the decided time, under a specific load 250gm . A specially designed brushing device was used with electric tooth brush. Then all the specimens were re-measured after brushing for the detection of the post-brushing surface roughness (Ra2) , and the results are represented in table (3 ) .
Data analysis was performed in several steps. Initially, descriptive statistics for each group results. Three factors analysis of variance ANOVA test of significance comparing variables affecting roughness; composite, brush type and brushing time. One way ANOVA followed by pair-wise Newman-Keuls post-hoc tests was performed to detect significance between brushing time. Then separate student t-test to detect significance between brush type and composite. P values ≤ 0.05 are considered to be statistically significant in all tests.
The results revealed significant (ًp<0.05) influence of composite type (Methacrylate > silorane) on surface roughness mean values, a significant (ًp< 0.05) influence of the bristle type (Medium > soft) on surface roughness mean values. The effect of brushing time (15 min.> 10 min.> 5 min.) was statistically significant (p<0.05),table( 12),figure(18).
Under the conditions of this study, the following conclusions can be drawn:
1. The toothbrushing directly affects the surface roughness of the composite formulations.
2. Different types of toothbrush bristles affect the surface roughness of resin composite restorations differently.