الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
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Abstract
For decades, the first objective of anterior dental restorations has been to
replace tooth structure lost by dental disease in an esthetic manner. Improvements of dental
techniques and materials have led to development of all ceramic restorations which are well suited
to change the shape and color of teeth Laminate veneers provide a conservative elegant esthetic
solution.
Veneers have been introduced with different materials and techniques which resulted in improvements
in color, translucency and fracture resistance of the teeth (1).The main drawback of the laminate
veneer restoration was its susceptibility to fracture and color matching. It was revealed that
fracture in porcelain veneers seems to be associated with incisal preparation designs and change in
bonding conditions. (2, 3)
Crystal High Translucency restorations are the most translucent zirconia materials available,
allowing 20-30% more light to pass though than other zirconia materials. Restorations can be used
to create bridges that are up to five times stronger than other ceramic restorations currently
available while providing life-long strength plus the esthetic qualities patients seek.
Lithium-disilicate glass ceramic is a type of glass ceramic commercially known as IPS e.max. The
crystals that form within this material are contributing double the fracture strength and fracture
toughness of the lithium disilicate glass materials. This material can be very translucent even
with high crystalline content: this is due to the relatively low refractive index of
lithium-disilicate crystals. This material is translucent enough that it can be used for
full-contour restorations or for the highest esthetics, can be veneered with special
porcelain (4).Dental restorations using all ceramic materials in association
with adhesive cements have become popular, primarily because of esthetic
properties such as translucency, fluorescence and opalescence that better
simulate the appearance of natural dentition, other desirable characteristics
include chemical stability biocompatibility and high compressive strength.(5)
In1999, Magne and Douglas (6) introduced a new approach for adhesive
bonding of ceramic veneer. With the new method the dentin bonding is
applied and cured immediately after completion of tooth preparation, before
the final impression is taken in situation that lead to significant dentin
exposure and subsequently affect the bond ,for this situation technical
challenge in bonding procedure are performed by recent study of Yu-Sung
Cho in 2010 to evaluate the effect of immediate dentin sealing on the bond
strength of resin cement to porcelain restoration showed improvement in the
bond strength compared to conventional method.Consequently, this study
was undertaken to evaluate the effect of two preparation designs on the
color translucency and fracture load of two ceramic materials cemented by
two methods.