الفهرس 
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Abstract
The current study investigated the enamel wear behavior and surface roughness opposing two new translucent zirconia; KATANA STML and KATANA UTML with two surface finishing procedures (glazed and polished).
Two groups were tested according to the material to be used; group A: super translucent zirconia (Katana STML), group B: ultra-translucent zirconia (Katana UTML). Each group was divided into 2 sub-groups: glazed and polished. Each sub-group consisted of 7 zirconia specimens and 7 enamel antagonists. A third group of natural enamel was used as a control group. Zirconia specimens were cut in the form of discs of diameter = 12mm, and thickness = 5mm. Concerning the enamel antagonists; buccal cusps were isolated from intact human premolars. A toothbrushing machine was used for the wear test. It simulates the jaw movement during chewing by performing horizontal movements with the application of a vertical load. The zirconia specimens and the enamel antagonists were subjected to 120,000 strokes with vertical load 49N. The amount of wear was determined based on weight loss percentage. The enamel antagonists were weighed before and after the test by analytical digital balance. The percentage of wear was determined from the following equation: Wear (percent weight loss) = ΔW x 100/ W1. Concerning the surface roughness; Qualitative and Quantitative analysis of the specimens and their antagonists was carried out before and after loading using 3D laser scanning confocal microscope.
The results showed that the polished UTML and STML zirconia caused significantly less antagonist wear than the glazed UTML and STML zirconia. While the natural enamel showed the highest antagonist wear. There was a significant increase in the surface roughness of the zirconia specimens and the enamel antagonists after the wear test.
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Within the limitations of this study, UTML zirconia is more effective in decreasing the antagonist enamel wear compared to the STML zirconia. UTML zirconia could be the material
of choice instead of STML zirconia to lower the enamel antagonists’ surface roughness.