الفهرس 
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Abstract
This study was designed to compare the fracture resistance and shade
accuracy of two types of zirconia crown fabricated by two different techniques
Bilayered CAD- on technique (CAD/CAM-fabricated zirconia core veneered
with CAD/CAM-fabricated lithium-disilicate glass-ceramic veneering
material) and CAD/CAM zirconia monolithic full contouring technique
supported by zirconia implant abutment and titanium implant abutment.
Twenty four titanium implants with a diameter of 3.7 mm and a length
of 11.5 mm will be embedded with student acrylic model to replace the
missing maxillary first premolar guided by the manufacturer’s instructions.
This study is divided into two group according to the types of
abutments that were used (Titanium straight abutments, Zirconia straight
abutments) twelve for each. The abutments were 4.5 mm diameter, the
abutment screws were tightened to 35 N-cm with a hex driver and a calibrated
torque driver.
Each group will be divided in to two subgroups according to the type
of zirconia crown used, Bilayered CAD- on crown and CAD/CAM
monoblock crown.
Two types of zirconia crown were cemented to the abutments using the
Variolink cement as a try-in past.
Aspectrophotometer was used to measure the shade accuracy and the
universal testing machine for measuring the fracture resistance through:
1- Bilayered CAD- on crowns on titanium and zirconia dental implant
abutments.
2- Full contoured CAD /CAM monoblock crowns on titanium and
zirconia dental implant abutments.
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