الفهرس 
• IntroductionOnly 14 pages are availabe for public view
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Abstract
Summary
Reproducing the intraoral relationship of implants through impression procedures is the first step in achieving an accurate, passively fitting prosthesis. The critical aspect is to record the 3-dimensional orientation of the implant as it occurs intraorally, along with reproducing fine surface details.
Therefore, improper recording of the fine details in impressions results in inaccurate cast that will affect superstructure fit resulting in mechanical and biologic consequences that disrupt the function of dental implants.
The research presented in this study evaluated effect of two impression techniques and two impression materials on the passivity of fit of implant supported prosthesis.
A model of cast acrylic sheets was constructed by laser cutting machine and 2 holes were drilled in the center of its top surface by a drilling machine for the insertion of 2 implants.
The 2 implants were inserted in the 2 holes perpendicular to the top surface of the master model surface simulating the clinical situation of missing lower second premolar.
Custom made trays were fabricated for each open and closed impression techniques to fit the master model from cast acrylic sheets.
Impressions used were divided into two main groups according to the impression technique. The two main groups were:
• group (1): open tray impression technique.
• group (2): closed tray impression technique.
Each group was further subdivided into two subgroups according to impression material used:
• Subgroup (A): polyvinylsiloxane in medium consistency
• Subgroup (B): polyether in medium consistency
For the open tray impression technique (group 1); Open tray impression copings were adapted and fastened to the implants using the coping screw. The impression material was applied according to the manufacturer’s instructions. Both impressions were applied respectively. After polymerization of the impression, screws were loosened and the tray was removed from the master model with the transfer copings in it. Implant analogs were connected to each transfer coping present in the set impression. The impression was poured and the resultant cast was used as master model.
As for the closed tray impression technique (group 2); after polymerization of the impression, the tray was removed from the master model but without the transfer copings. Impression copings were unscrewed from the implants & removed one at a time then fastened to each analog matching its size using the screw. Thus, the analog/coping assembly was connected and inserted in the set impression firmly. The impression was poured and trimmed to produce a master model.
The wax frameworks were constructed using CAD/CAM technique.
Casting of the wax frameworks into metal frameworks was done using traditional wax burn out and casting procedures.
The assessment of the passivity of fit of the bridges was performed using bonded elastic resistance strain gauge technology. 4 Strain gauges were mounted to the mesial and distal coronal part of the implant surface.
Each sample was individually seated on the master model and vertically mounted in the lower fixed compartment of a computer controlled materials testing machine with a load cell.
A 10 N load was applied on the bridge’s pontic central fossa. The force applied was with a custom made load applicator attached to the upper movable compartment of the machine.
The strain gauge foils connected to a strain meter recorded the strain & revealed the graph on the computer’s screen then analyzed the output using computer software.
The data obtained were collected, tabulated and then subjected to statistical analysis. The results showed that there is no difference between the two impression techniques (open-closed) & between the two impression materials (polyether-addition silicone) on the passivity of fit of implant suprastructure.