الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The purpose of this study was to evaluate the sealing ability of Portland cement and MTA in comparison to amalgam as retrograde filling materials by utilizing three
different root - end preparatory methods ( Laser ,ultrasonic and conventional techiques ) . One hundred and twenty eight teeth were used divided into three main experimantal groups (n=36) : (1) diode laser preparation (L) (980nm 8 w\10 sec