ABSTRACT
The purpose of this study was to compare the flexural strength and marginal accuracy of a newly introduced Y/Zr Inceram bridges made from Yitrium Zirconia ready made ceramic blocks and constructed by computer controlled milling and sintering Cerec in Lab technique, against Al Zr/ Inceram bridges constructed by the conventional slip cast techniques as a control. Fourteen three-unit FPDs substructures were fabricated: Seven three-unit FPDs substructures were fabricated from Yitrium Zirconia ready made ceramic blocks using the Cerec In Lab technique and seven were constructed from Al Zr/Inceram using the conventional slip cast technique. An Instron testing machine was used to evaluate the flexural strength of the two types of bridges; where a load was applied perpendicular to the long axis of the substructure, in the middle of the occlusal surface of the pontic until failure. The marginal accuracy of the tested substructures was measured using a traveling microscope. Values were recorded and statistically analyzed. Results showed that the highest flexural strength values, exceeding 700 MPa, and the highest marginal accuracy were achieved with Y/Zr Inceram bridges that were constructed using computer controlled milling and sintering Cerec In Lab technique. The differences in mean values were statistically significant with a p-value <0.0001. So it was concluded that the high flexural strength and marginal accuracy record by Y/Zr Inceram bridges constructed using Cerec In Lab technique indicates that it could be useful for highly loaded all-ceramic restorations, especially in the molar region