الفهرس 
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Abstract
This study was designed to investigate, in vitro, the cervical marginal accuracy and fracture characteristics of all-ceramic Zirconia posterior cantilever bridges (CAD / CAM milling, Cerec inLab) using different connector dimensions. Materials and methods: Specially designed stainless steel model was constructed and a total number of 20 posterior cantilever bridges were constructed and classified into four equal groups, five each, according to connector dimensions. The first group of FPDs was constructed using Metal-Ceramic technique, with 3x3 mm connector area dimension. The second group of FPDs was constructed using Zirconia, with 4x3 mm connector area dimension. The third group of FPDs was constructed using Zirconia, with 3.5x3mm connector area dimension. The fourth group of FPDs was constructed using Zirconia, with 4.5x3mm connector area dimension. The samples were tested to determine the cervical marginal accuracy using USB Digital microscope. Fracture pattern was then observed and microscopic examination of randomly selected fractured bridge sample from each tested group was carried out using scanning electron microscope. Results: Metal-ceramic group showed statistically significantly higher mean cervical marginal discrepancy (40.7 ± 13.1 µm) than Zirconia group (26.1 ± 7.5 µm). Conclusions: the four tested groups had acceptable marginal fit and strength, which leads to clinical success. Posterior bridges made from Sirona inCoris ZI using (CAD / CAM milling, Cerec inLab) are with more marginal accuracy but less in strength than those made of metal-ceramic using (Conventional lost wax). The connector dimension plays a major role in reducing the stress values, as fracture load increased when cross-sectional area of the connector became larger. Zirconia can present interesting alternative to replace metal-ceramic posterior cantilever bridge and can therefore encourage further clinical investigation.