الفهرس 
Fracture resistance of occlusal veneers made from hybrid ceramic (Cerasmart) with two different thicknesses :In vitro study
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Abstract
The purpose of this in-vitro study was to compare the fracture resistance of occlusal veneers made from hybrid ceramic (Cerasmart) with two different thicknesses. Twenty four human first maxillary molars were used in this study. Extracted maxillary first molars were collected from patients with untreatable periodontal problems (grade III mobility); Teeth were chosen to be free from any caries, defects or Cracks. To facilitate standardization of tooth position during occlusal veneers preparation and during the test procedure, teeth were mounted in epoxy resin blocks. The teeth were position in the center of the block, parallel to its long axis and perpendicular to its base. A specially designed centralizing device was constructed to allow the accurate placement of the teeth during fabrication of the epoxy resin block. Teeth were randomly divided into two main groups (12 each). According to the hybrid ceramic material thicknesses table (2) and Figure (12). group A - (n= 12) (control) Teeth were prepared to receive Cerasmartocclusal Veneers with 1.8 mm thickness at the cusp tip and 1.2 mm at the central groove. group B {u2013} (n= 12) (intervention): Teeth were prepared to receive Cerasmartocclusal veneers with 1.3 mm thickness at the cusp tip and 0.6 mm at the central groove.A standardized tooth preparation was applied to all specimens using CNC milling machine, with anatomical occlusal surface preparation with 1 mm ferrule and 1mm deep chamfer finish line.Then occlusal veneers were fabricated by CAD/CAM milling using The CEREC AC system. Then all occlusal veneers were checked over their corresponding teeth for Seating. The internal surface of the restorations was rinsed with water and air dried, and then sandblasted with 50 æm aluminum oxide particles.The internal surface of all restorations was then silanized using silane coupling agent for 60 s then air dried for 5 sec