Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

The present study evaluated the vertical marginal gap distance of recently introduced monolithichighly translucent zirconia crowns compared to veneered translucent zirconia with two different finish lines (shoulder and deep chamfer). A total of twenty four (n=24) crown samples were constructed frommonolithic highly translucent zirconia (n = 12) and veneered translucent zirconia {u200E}(n = 12) {u200E}using CAD / CAM system on specially designed stainless steel die (8mm cervical diameter, 6mm occluso gingival height and 15-degree total occlusal convergence). The preparation ended with either: 1mm shoulder finish line or 1mm deep chamfer finish line. The crown samples were then divided into two equal groups: Group I: (n = 12) monolithichighly translucent zirconia (zirkonzahn prettau zirconia). Group II: (n = 12) veneered translucent zirconia (zirkonzahn Ice zirconia). Each group was then subdivided into two equal subgroups: Subgroup 1: (n = 6) shoulder finish line. Subgroup 2: (n = 6) deep chamfer finish line. 24 Impressions form the stainless steel dies were made using a cylindrical copper perforated tray, these impressions were then poured into type IV improved dental stone to obtain an exact replica to the stainless steel dies. The stone dies received monolithichighly translucent zirconia crowns (prettau) (n = 12) and veneered translucent zirconia crowns (ICE zirconia) (n = 12), with two different finish line designs (shoulder (n = 6) and chamfer (n = 6)). Veneering of the translucent core was done using the layering technique.And after definitive sintering for both groups, the vertical marginal gap distance of all samples was tested by using a stereomicroscope, and the data were tabulated and statistically analyzed

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