الفهرس 
Phase transformation toughening (PTTOnly 14 pages are availabe for public view
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Abstract
Keywords: flexural load, fracture resistance, implant-supported prosthesis,
bi-layered zirconia, monolithic zirconia.
Purpose: to investigate the flexural strength and the fracture loads of bilayered
and monolithic zirconia implant supported FDPs.
Materials and methods: For flexural strength test, two groups of bar-shaped
(25 × 5 × 2 mm3) monolithic zirconia (n=5) and bi-layered zirconiaporcelain
(n=5) specimens were prepared using CAD/CAM system for
zirconia and hand layering for porcelain. Flexural strength test was
performed using universal testing machine at cross-head speed of 1mm/min.
For fracture resistance test ,twenty master models composed of two implant
analogues and their corresponding titanium implant abutments embedded
vertically in auto-polymerizing acrylic resin blocks to mimic clinical
conditions for a four-unit FDPs. Twenty FDPs were fabricated and divided
into two groups (n=10); group (A)bi-layered zirconia four-unit implant
supported FDPs. group (B) monolithic zirconia four unit implant supported
FDPs. Samples in each group were cemented to their corresponding model
and then underwent artificial ageing by thermo-cycling of 5000/cycle. The
fracture resistance test was done using universal testing machine at crosshead
speed of 1mm/min. Statistical analysis of the results and comparison
between each two groups were performed using independent t-test
(significance (p< .05).Results: monolithic zirconia group recorded
statistically significant higher flexural strength and fracture resistance
compared to bi-layered group. Conclusion: strength of monolithic zirconia
is significantly higher than bi-layered zirconia.