الفهرس 
Surface Roughness and Color Change of Machinable Ceramic, Composite and Hybrid Blocks Before and After Erosion and/or Abrasion Challenge: In Vitro Study
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Abstract
This in vitro study was carried out to assess the surface roughness and color change of machinable ceramic, composite, and hybrid blocks before and after erosion and/or abrasion challenge. A total of 90 specimens of Ceramic, hybrid and composite CAD/CAM blocks were tested in the study. The specimens were divided into three main groups of 30 specimens each, then subdivided into 3 subgroups of 10 specimens each according to challenge. First, Erosion challenge; where specimens were exposed to pepsi-Cola for 5 min, three times per day for 7 days. Second, Abrasion challenge; where half of the specimen of this subgroup were subjected to the abrasion using Oral-B cross action power max powered toothbrush with a dentifrice (Colgate® total advanced fresh) that has RDA of 160 for one minute twice a day for 7 days, while the other half was subjected to toothbrush abrasion without toothpaste. And third, Erosion/Abrasion challenge where the specimens were subjected to an erosive followed by an abrasive challenge either with or without an abrasive toothpaste. For each specimen, A spectrophotometer was used to record the color and an optical profilometer was used to record the surface roughness before (baseline) and after the erosive and/or abrasive challenge. Color differences (xE) and surface roughness (Ra) were then calculated and statistically analyzed using Three-way ANOVA and Bonferroni{u2019}s post-hoc test. Pearson’s correlation coefficient was used to determine the correlation between surface roughness and color change. The Color change (xE) results revealed that, regarding the effect of block material, there was insignificant difference between the 3 block materials, except after Erosion + Abrasion with toothpaste where composite blocks showed significantly higher xE than ceramic and hybrid blocks, with insignificant difference between the latter two. Regarding the challenge, Erosion + Abrasion showed the statistically significantly highest mean xE than Erosion, while Abrasion showed the statistically significantly lowest mean xE. While for the use of toothpaste, using ceramic, composite or hybrid after Abrasion or Erosion + Abrasion, the mean (xE) without toothpaste showed significantly lower mean value than with toothpaste. Regarding the surface roughness results, with different challenges either before or after brushing, without or with toothpaste; there was no statistically significant difference between mean (Ra) of the three materials