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

The aim of this study was to evaluate the effect of the crystallization process on the fracture resistance and failure mode of two forms of zirconia reinforced lithium silicate CAD/CAM fabricated crowns, by comparing the fracture resistance and failure mode of the partially crystallized form (VITA SUPRINITY®) to the fully crystallized form (Celtra® Duo). According to sample size calculation, a total of sixteen restorations were constructed. The samples were divided into two equal groups, eight samples for each group according to the material type used: Group (S): Eight crowns samples (n=8) fabricated of VITA SUPRINITY® CAD/CAM blocks -Group (C): Eight crowns samples (n=8) fabricated of Celtra® Duo CAD/CAM blocks. An acrylic right first mandibular molar was prepared according to regular dimensions of all ceramic restorations preparation guidelines with an occlusal reduction of 1.5 mm, axial reduction of 1mm, circular shoulder finish line of 1mm thickness with rounded internal angle and 6 degree occlusal convergence angle. Preparation was performed manually by an experienced practitioner and the bucco-lingual and mesio-distal convergence angles of the tooth preparations were checked and confirmed by using dental surveyor. The prepared acrylic tooth was then duplicated into sixteen epoxy resin dies using silicon impression material. The prepared acrylic tooth was scanned by 3 shape D500 extra oral scanner and then milled by Sirona MCX5 milling machine using VITA SUPRINITY® blocks and Celtra® Duo CAD blocks to produce eight VITA SUPRINITY® crowns and eight Celtra® Duo crowns respectively. After milling, VITA SUPRINITY® restorations were crystallized in a ceramic furnace (programat P300) to reach the fully crystallized form. VITA AKZENT plus glaze was then used for glazing of the VITA SUPRINITY® restorations while glazing of Celtra® Duo crowns was performed with Densply Sirona universal overglaze

Issued also as CD