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Abstract
This study aimed to evaluate three systems used to produce dental
crowns; gold electroforming system GES, In-ceram alumina all ceramic system
and the conventional metal ceramic system using gold alloy. Laboratory
evaluation aimed to evaluate the shear bond strength SBS between veneering
porcelain and underlying structure through making disc shaped specimens from
the core materials and veneering porcelain in the form of rods. The change in
color between intended shade guide and the resulted one, the marginal and
internal fit of the tested systems was conducted through making 10 crowns of
each system. The color change was evaluated using a recently introduced
intraoral spectrophotometer, the marginal fit prior and after cementation was
measured using a travelling microscope and sectioning of crowns was done to
study the internal fit of each crown. The second part of the study aimed to
evaluate 15 produced restorations clinically. Results of the study revealed that
the shear bond strength between the veneering porcelain and underlying structure
was significantly different among the three tested groups, with the gold alloyceramic
restoration showing the highest values (31.7 MPa) , followed by the
GES ( 24.9 MPa) and finally the In-ceram alumina ( 17.8 MPa). The change in
color between the intended shade (2M2 -3D-master ) and the resulted color
showed Delta E of 1.56 for the metal ceramic, 1.21 and 1.23 for the GES and Inceram
alumina all-ceramic respectively. Marginal and internal fit showed high
significant difference between the three tested groups with the GES showed the
least marginal and internal gaps followed by the metal ceramic and the In-ceram
alumina respectivley. Clinical evaluation of the three systems showed a 100 %
survival for metal ceramic crowns, 80 % for both the GES and the In-ceram
Alumina during a period of 17 months. It was concluded that the metal ceramic
and the GES produced acceptable shear bond strength to the veneering porcelain.
While the In-ceram showed values less than the acceptable ones. The change in
color for the three groups falls within the clinically acceptable range.