الفهرس 
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Abstract
Surface roughness was proven to have a critical importance regarding the esthetics and durability of resin composite restorations. Surface roughness affected by many factors including the type of resin material, the finishing and the polishing methods. This study was conducted to evaluate the effect of different polishing methods on the surface roughness (Ra) of two scalpel finished composite resins.
A total of 72 disc samples were prepared from nanofilled (Filtek Z350XT,3M ESPE,St Paul, USA) and nanohybrid (Filtek Z250XT,3M ESPE,St Paul, USA) composite resins using split Teflon mold and cured against Mylar celluloid strip. The samples were divided into two main groups (n = 36), The first group (A1) nanofilled and the second group (A2) nanohybrid resin composite. Each main group was divided into six sub groups according to the finishing and polishing tool used (n=6). Then with exception of the control group (B0) all specimens were finished with scalpel blade placed at 45 degree to the specimen in a peeling motion in one direction (10 strokes) with light pressure.
The scalpel finished samples then subdivided into 5 subgroups (n=6) B1(Scalpel finish), B2(Sof-Lex Extra Thin Polishing discs), B3(Sof-Lex Spiral wheels), B4(Sof-Lex polishing strips), B5(Polishing paste and brush). All samples were scanned using scanning electron microscope (SEM), and the images were subjected to Gwyddion 2.59 software (SPM data visualization and analysis tool, supported by the Czech Metrology Institute, 2019) to attain Surface Roughness Average Ra data, which were statistically analyzed by two-way ANOVA and Tukey Post Hoc test. Representative samples from each group were randomly selected to qualitatively evaluate the resin composite samples surface.
There was a significant interaction between the resin composite material and the polishing protocol (p=0.002). Nano hybrid A2 had a significantly higher value than nano filled A1 (p<0.001). And between the different finishing and polishing methods, there was a significant difference between different groups (p<0.001). The highest value was found in B1, followed by B4, then B2, B0 and B5, while the lowest value was found in B3.
Within the limitations of this in vitro study, the following conclusions could be suggested:
1- Scalpel is a good finishing tool for resin composite to produce a smoother micro surface ready for polishing.
2- The nano filled resin composite produces a smoother surface than nano hybrid resin composite with different polishing methods.
3- Sof-lex spiral wheels are the best polishing tool for nano filled resin composite.
4- Polishing paste and brush are the best polishing system for nano hybrid resin composite.
Clinical Recommendation:
Scalpel finishing technique provided a pre polished smoother micro surface free of scratches and cracks ready for polishing and can be clinically considered as a tooth friendly way for finishing resin composite restorations.