الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The purpose of this in-vitro study was to compare the fracture resistance of lithium disilicate endocrowns with circular post and endocrowns with H-shaped short post when bonded to endodontically treated premolar teeth .
In the present study 22 extracted single rooted premolars (specimens), were divided into two equal groups (11 specimens in each group).
group H : restored with endocrowns with H- shaped post.
group C : restored with endocrowns with circular post .
To facilitated standardization of the teeth position during endocrown preparation and during test procedures, all teeth were mounted in epoxy resin blocks were positioned in the center of the blocks, parallel to its long axis and perpendicular to thier bases.
Teeth were decapitated 2 mm above the cementoenamel junction from the proximal surfaces , then endodontically treated .
Teeth were prepared to recieve either endocrown with H- shaped post or endocrown with circular post .
Teeth were scanned with DOF scanner and restorations were designed with EXOCAD software . All restorations were milled with imes-icore machine.
All endocrowns were checked on their corresponding teeth for cracking, proper seating and marginal accuracy .
The endocrowns were cemented on their corresponding teeth using BisCem (Bisco Inc.,Schaumburg, IL, USA) dual-cure adhesive resin cement following total etch technique protocol.
The endocrowns were seated into the prepared teeth with finger pressure and excess cement was removed with a microbrush. Then, the samples were maintained under a constant load of 3 Kg using aspecially designed loading device to standardize the load applied during bonding procedure.
All samples were subjected to fracture resistance testing under a compressive load at the center to their long axis using controlled universal testing machine with a load cell of 5 kilo newton (KN) and at a crosshead speed of 1 mm/min. After facture testing, fracture patterns and failure mode of all samples were examined visually and
photographically by digital camera.
Data were collected and statistically analysed.