الفهرس 
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Abstract
Sintering process is a crucial stage in the fabrication of dental zirconia, which has
been lately produced as a high strength ceramic core material for fixed dental prosthesis. It
can be sintered in variant parameters and different sintering furnaces, either by
conventional sintering furnaces in a long cycle, or faster sintering furnaces.
The objective of this in vitro study is to assess the effect of speed and high speed
sintering of monolithic zirconia restorations, compared with conventional sintering
technique as regard dimensional changes after sintering, crystal structure, and bi-axial
flexural strength.
Thirty six disc specimens of 12mm diameter and 1.5mm thickness were fabricated
from pre-sintered Multi-Layered katana zirconia blank using DWX-50,Roland DG milling
machine, and based on sintering technique , three groups (n=12) were created. group I:
Conventional sintering (CS): specimens were sintered at 1500 °C, starts at room
temperature. Total time is approximately 10 hours. group II: Speed sintering (SS):
specimens were sintered at 1515 °C, starts at room temperature. Total time is
approximately 90 minutes. And group III: High-speed sintering (HS): begins at 1580 °C
and has a dwell time of 10 minutes. Specimens were removed from the furnace immediately
after sintering. Total time is 10 minutes.
For each sample, pre and post sintering dimensions were measured by digital
micrometer (within the accuracy of 0.001mm) with respect to diameter and thickness for
estimating the linear shrinkage.
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Three discs were selected randomly from each group for detection of microstructural
crystalline phase content present by X-ray diffraction. Samples were subject to Cu-K alpha
radiation with values of 2θ= 20°- 80°, diffraction profiles were performed at 2°min-1.
According to ISO 6872 standards, the ball-on-ring design was used to conduct the
biaxial flexural strength test. The test was performed using a universal testing machine,
and Biaxial flexural strength was calculated in MPa by measuring the fracture load.
It was shown that all groups demonstrated a uniform 20% shrinkage in all
dimensions upon sintering, which is equivalent to the manufacturer’s requirements.XRD
analysis revealed that all of the tested samples showed characteristic peaks of tetragonal
and cubic phases. There was no significance changes observed among the groups regarding
bi-axial strength values.
It was therefore concluded that speed and super speed cycles can be recommend for
sintering of monolithic zirconia in order to reduce fixed prosthetic restoration fabrication
times as the changes they induced were within the clinically acceptable ranges.