الفهرس 
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Abstract
Study the effect of different impression transfer techniques for four implants on the passive fit of multiple bars used to retain\support mandibular implant assisted overdenture, methodology: Six patients already received four mandibular implant supported overdentures (multiple bars connecting the four implants) were selected. Pick up impression for the bar framework will be done and poured as a control cast. Three different impression techniques were done for each patient; Technique 1: short transfer impression copings were used for a closed tray impression. Technique 2: long transfer impression copings were used for open tray pick up impression. Technique 3: long transfer impression copings splinted with prefabricated acrylic resin bars were used for open tray pick up impression Evaluation: the passivity of each framework was evaluated 1) clinically: by one screw test 2) laboratory: by recording a pick up impression for the bar framework and pouring a control cast, the positional changes of the implant analogs after each impression transfer technique was measured by a digital scanning approach.