الفهرس 
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Abstract
Two designs of inlay retained fixed partial denture (IRFPD) preparation.Occluso-mesial and occluso-distal box(OD/OM), and mesio-occluso-distal (MOD) retainers were studied, with two different spaces of the pontic (7 and 9 mm) to restore upper second premolar.
Four inlay retained fixed partial dentures (IRFPDs) were constructed using fully contoured CAD/CAM Zirconia blanks.
Fracture resistance of the different models was performed usiung universal testing machine.
The results showed that OD/OM designs had stasistacially higher fracture resistance values than MOD inlay design, the mean of the fracture resistance samples of model one was the highest recorded value (2787.3±34.2 N) while fracture resistance of model two was (1661±38.3N) and model three was (2696.4±48.4N) ,while model four show the lowest fracture resistance (1257.5±35.5N). The models of 7mm pontic span showed higher fracture resistance value than 9mm pontic span models regardless of design of inlay retainer, yet,two surface inlay retainer showed higher freacture resistance than MOD inlay retained fixed partial denture in both studied pontic span lengths.
Consering the studied mode of fracture, there were no observed differances between the studied models as there was no specific type of fracture. Fracture of all models occurred at molar-pontic connector and or the retainers. two specimens of model four had fractured at both molar and premolar connectors.
Scanning the four models were performed in order to get four 3D finite element models to compare the stress generated on the components of IRFPDs restored by lithium di-silicate ceramics and Zrconia. Two force directions (vertical and oblique 30º from buccal side) applied at central fossa of pontic, maximum stresses generated in each model was calculated. Result showed that Zirconia fixed partial denture had higher fracture resistance value than lithium di-silicate ceramics either in vertical forces or oblique forces.
This study gave an idea about the material of choice used in case of IRFPD cases is Zirconia as the maximum stress of the restoration increased in long span pontic or in oblique forces.