الفهرس 
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Abstract
The introduction of yttrium partially stabilized tetragonal zirconia
polycrystal (Y-TZP) to the dental field opened the design and application
limits of all-ceramic restorations with greater confidence and success
rates. With its superior mechanical properties, three or four-unit fixed
partial dentures (FPDs) are no longer the safe limit for the construction of
core veneered all ceramic restorations. Establishing a strong and stable
bond with Zirconia has proven to be difficult, as the material is acid
resistant and does not respond to common etching and silanation
procedures used with other glass containing ceramic materials which react
to silane coupling agents. As Zirconia is relatively opaque and
monochromatic in colour, a layer of veneering ceramic is built on to
provide the restoration with the required esthetics. Low-temperature
degradation (LTD) has been associated with several 3Y-TZP-based
biomaterials. The bond between veneering ceramic and Zirconia
framework is currently the subject of comprehensive investigations.
Thus the purpose of this study is to investigate the effect of a new
method of surface treatment of Zirconia on its bond strength with the
ceramic veneering ceramics with different veneering techniques and with
and without s-LTD aging.
A total of 144 microbars were prepared. Each 36 have received a
different surface treatment namely: no treatment (control), Air Abrasion
with 110μm aluminum oxide particles (Al2O3), Silica infiltration with
silicate compound and heat, and acid etch with a mixed solution of HF
and HNO3.Then each 36 were further divided into three groups each 12
received different veneering technique Layering, Sintering CAD on technique and Adhering CAD on technique. Then each 12 microbar were
divided into two groups were one group didn’t receive any treatment and
the other groups were aged using s-LTD aging in an autoclave at 134ºC
for 6 hours. The bars were attached to a specially designed attachment and
tested in the universal testing machine (LLOYD). The load required for
fracture of each specimen was recorded in MPa. Data were presented as
mean and standard deviation (SD) values, a regression model using threeway
Analysis of Variance (ANOVA) was used in testing significance for
the effect of surface treatment, veneering technique, aging and their
interactions on mean micro-tensile bond strength. Tukey’s post-hoc test
was used for pair-wise comparison between the groups when ANOVA test
is significant. Fractured microbars viewed under digital microscope with
magnification 40X and type of failure was specified recorded as number
and percentage in each subgroup.
The results of this study revealed that that surface treatment,
veneering technique, aging and the interaction between the three variables
had a statistically significant effect on mean micro-tensile bond strength.
Air abrasion showed statistically significant same mean micro-tensile
bond strength as that of Control, Silica infiltration higher than control
whereas acid etched lower than control. Sintering CAD-on showed
statistically significant higher mean micro-tensile bond strength than both
Layering and Adhering CAD-on veneering technique. Aging showed
statistically significant higher mean micro-tensile bond strength than
Without Aging.