الفهرس 
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Abstract
Based on the fact that proper finishing and polishing of dental restoration was found to be of critical importance in regard to their resulting aesthetics and longevity. This study was conducted to evaluate the effect of the multiple use and sterilization of Single Step polishing tips on the Surface Roughness (Ra) of resin composite.
In total, 80 Nanofilled resin composite discs were prepared using split Teflon mold, and cured against Mylar celluloid strip. Except for control group, samples were wet ground against 600 grit SC paper for 30 sec. After which they were divided into 3 main groups (n = 25), where group D (Dimanto® - VOCO), group G (PROGLOSS™ - KaVo Kerr), and group O (OptraPol® - Ivoclar Vivadent) polishing systems. Five disk-shaped Single-Step polishing tips from each system were sterilized and used for resin composite sample polishing (30 secs, following the manufacturer instruction), and this process was repeated for 5 successive Reuse and Sterilization cycles (S1 - S2 - S3 - S4 - S5) on different 5 samples each time. Scanning electron microscope (SEM) was used to scan all samples, and the images were subjected to Gwyddion 2.53 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.
The Single-Step Polisher system and the Reuse and Sterilization cycles as well as the Polisher system/Reuse and Sterilization Cycle Interaction where found to have a statistical significant effect on the surface roughness average Ra of the tested groups (P < 0.0001). The control group had the least statically significant Ra. All the first reuse and Sterilization Cycle Groups (GS1, OS1, DS1) as well as, two of the second reuse and Sterilization Cycle groups (GS2, OS2), showed higher Ra without statically significant difference neither between them nor between them and the control group. While the GS4, GS5, DS5, and Roughened groups, showed the highest Ra with no statically significant difference between them.
Under the limitations of this study, the following conclusions could be suggested:
1. Single-step reusable polishing tips can polish resin composite back to matrix-set Ra values within the first and second reuse/sterilization cycles.
2. Afterwards the tips’ polishability decreases significantly and becomes system dependent, yet none of the study groups exceeded the clinically accepted surface roughness values .