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Title: Reducing the alloy thickness of base metal ceramic restorations
Authors: Le Roux, Andre Rayne
Keywords: Metal alloys;Dentistry;Tooth preparation
Issue Date: 2009
Publisher: Dental Technicians Association of South Africa
Reduction in base metal alloy thickness will permit
additional porcelain depth and improved aesthetics
but unfortunately little information exists regarding
the thickness to which base metal alloys may be
reduced in comparison to noble metal alloys for
metal ceramic restorations. Even with comparison of
noble metal alloys the aesthetic benefits are restricted
to improving aesthetics in base metal restoration
further, since noble metal alloys are generally
regarded as providing superior aesthetics to base
metal restorative alloys.
The objective of this study was to determine whether
a significant reduction in thickness could be achieved
using a base metal alloy as compared to a noble
metal alloy and the thickness to which base metal
alloy substructures could safely be reduced while
still providing the same resistance to fracture of the
Material and methods:
Tensile strength tests (N) of the modulus of rupture
of the porcelain were performed on 40 base metal
alloy (Wiron 99, Bego, Germany) and 12 noble
metal alloy rectangular specimens (5.8 mm wide
and 15.0 mm long) bonded to a standardized 1.0 mm
thickness of dentine Creation porcelain. The base
metal alloy thickness varied in 0.1mm increments
from 0.1 to 0.4 mm. The results were compared to
12 noble metal alloy (Bio Y 81, Argen, South Africa)
specimens of recommended minimum thickness
(0.3 mm). Data for the results was obtained using a
universal tensile testing instrument, which was set to
operate at a cross head speed of 0.5mm (Instron Mini
44, Instron corporation U.S.A). The applied force
(N) that measured the modulus of rupture of each
specimen was printed from a computer connected to
the Instron Mini 44 that operated on a 95% level of
confidence. Instron Agents (Durban, South Africa)
performed the calibration and setting up of the
machine prior to testing the specimens.
The results indicated a permissible 33.33% reduction
in the base metal alloy specimens as compared to
the noble metal alloy control specimens. This was
deduced from the reduction in alloy thickness of up to
0.2 mm for base metal alloy specimens as compared
to the 0.3 mm noble metal alloy specimens. The
recommended thickness to which the base metal
alloys could be reduced without distortion of the alloy
was also 0.2 mm. The one-way ANOVA showed a
level of significance of (α=05).
Originally published in: Southern African dental technology journal, Vol. 1, No. 2, 2009.
Appears in Collections:Research Publications (Health Sciences)

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