الفهرس 
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Abstract
Objective: To determine the changes in surface roughness and gloss of different composite restorative materials before and after laboratory toothbrushing simulation and compared the results to those of dental enamel. Materials and Methods: Eleven disc-shaped specimens (10 mm diameter × 2 mm thickness) were prepared from a nanohybrid resin composite (IPS Empress Direct); a nanofilled resin composite (Filtek Z350 XT); and a microhybrid resin composite (Filtek Z250) and finished /polished using OptiDisc system. All the specimens were subjected to 15,000 cycles of circular toothbrushing with a force of 2 N and a slurry of toothpaste (RDA 50) with a device for simulated toothbrushing. Enamel specimens of 2 mm thickness of 11 extracted anterior teeth were used as a control. The mean roughness (Ra) was measured using AFM and the surface gloss of the same specimens was measured using glossmeter at a specific angle of 60° at the baseline and after 60-minute of simulated toothbrushing. To compare the surface roughness and gloss of the different materials before and after toothbrushing, the collected data were subjected to statistical analysis using two-way analysis of variance (ANOVA), Student’s t-test and One-way ANOVA with Tukey’s post hoc tests. The level of significance was seated p<0.05. Results: The microhybrid resin composite showed the greatest increase in the mean roughness and the lowest surface gloss, while the nanofilled resin composite demonstrated the lowest increase in the mean surface roughness and highest surface gloss. A statistically significant difference in surface roughness and gloss were found before and after toothbrushing for the three resin composite materials (p<0.001). The results demonstrated an inverse relation between surface roughness and gloss. Conclusion: Simulated toothbrushing with slurry of toothpaste and distilled water significantly affected the surface roughness and gloss of the optimally polished resin composites but not tooth enamel. Microhybrid resin composite demonstrated rougher surface than nanohybrid or nanofilled composites with lower surface gloss.