الفهرس 
Concepts of ceramicsOnly 14 pages are availabe for public view
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Abstract
The present study aims of this study is to compare the effect of two
milling machines the Cerec 5-axis Mcx5 with the Cerec 4-axis Mcxl, on the
marginal adaptation of two all ceramic crowns using two different materials
the IPS Emax and Zirconia.
Acrylic lower second molars were selected and prepared using
straight hand piece mounted on surveyor, tapered stone with rounded end
was used to produce 1mm finish line and axial walls with 10 degree taper.
Twenty eight full contour crowns were designed on the scanned
abutments, using inLab 3D software (V4.2.5), and then were milled using
translucent zirconia blocks and lithium disilicate blocks, 5 crowns of each
material for every occlusal preparation design .
The translucent zirconia crowns were milled with an oversize of
approximately 25% to compensate for the later sintering shrinkage. The
crowns were sintered in high temperature furnace to have maximum density.
While the lithium disilicate crowns were adjusted in the pre-crystallized state
and then were glazed and crystallized.
The crowns were then seated and cemented. All crowns in all groups
were cemented with resin cement. During cementation static finger pressure
was applied then the specimens were axially loaded with a 5kg load using a
specially designed device.The vertical marginal gap was measured for all crowns using a digital
microscope fitted on a precision stand.
One Way ANOVA test was used to examine the effect of two milling
machines the Cerec 5-axis mcx5 with the Cerec 4-axis mcxl, on the marginal
adaptation of two all ceramic crowns using two different materials the IPS
Emax and Zirconia.
The results revealed that the lithium disilcate crowns showed better
marginal fit than the translucent zirconia, and because of the capability to
mill undercuts and minute anatomical details in multiple directions the
MCX5 showed better marginal adaptation than the MCXL.