Amir Saad Thesis final revision 03x - IUPUI

the margin of a crown was statistically significant between the two types of gold
previously mentioned, the findings were not clinically significant. 134
16
The incomplete fit of full cast crown restorations has been a problem for
dentists, which has led many researchers to study this problem. 135-139 Many
researchers have agreed that the use of a die spacer during fabrication of a full cast
crown improves the fit at cementation. 135, 138 Die spacers allow increased space
between the tooth surface and the internal surface of the casting. This reduces stress
areas created during cementation, and thereby resulting in a better fit and retention of
the final restoration. 135, 137, 138, 140, 141 It was believed in the past that frictional fit
between the coping and the tooth surface increased retention, 142 which makes a good
fit difficult when a die spacer is being used. 143-146 Die spacers should be applied in
layers according to the manufacturers’ instructions on the entire preparation on the die
down to 0.5 mm short of the preparation margin. 147
Grajower and Lewinstein 148 indicated that an optimum fit of the casting can be
obtained only if relief space allows for cement film thickness, roughness of the tooth,
and casting surfaces. They recommended a 50-µm spacer to compensate for the
cement film and surface roughness of the casting, which is around 30 µm, and for the
wax pattern distortion, which is about 20 µm.
Bronson et al. 122 found in his study that the clinically acceptable margins of a
cemented crown do not exceed 130 µm. Marginal adaptation was found to be
adversely affected by cyclic loading, which was correlated to the method of
149, 150
application of the core material.
ESTHETICS
Esthetics has always been a challenge in dentistry. One way to overcome this
challenge in endodontically treated anterior teeth is to make prefabricated esthetic