الفهرس 
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Abstract
This study was carried out to evaluate and compare the fracture strength of two different designs for restoring missing upper anterior teeth by resin bonded fixed partial denture.
Using ten bridges resembling conventional preparation which include reduction of maximum palatal area ending below the incisal edge with 2 mm and above the cervical line with 1 mm and extended to the proximal surfaces. Comparing with anther modified design using ten bridges in which reduced the retainer size to be confined at the cingulm area of the abutments and extended to the proximal surface with one retentive groove at each proximal surface in order to enhance esthetic by eliminating the gray color of the conventional design and increase the fracture strength.
An acrylic resin block was made by a ready-made plastic mold. Dental surveyor was used to ensure accurate vertical and centralized position of the root in the acrylic block.
All the preparation was done by the same operator and same devices .Bridges were cemented with resin bonded cement.
A Universal Testing Machine instrone was used to apply load at a crosshead speed of 0.5 mm/ min at 135° to the middle third of the palatal surface of the pontics until failure occurred.
There was significant difference within groups. Fracture strength results for both groups shown that the fracture strength means value for the group II was significantly higher than group I
SEM result showed that group II had 20% cohesive failure and 80% adhesive while group I had 40% cohesive failure and 60% adhesive failures.
Stress analysis result showed that all the stress the stresses concentrated on proximolingual areas –connector- , near the connector. Increase stress in model II within the retainer than model I while stress fallen on the abutments nearly the same.