Abstract
Statement of problem
Changing the internal design of a metal framework may decrease the manufacturing time,
the weight of the restoration, and the amount of alloy powder used, as well as simplify
the fabrication process.
Purpose
The purpose of this in vitro study was to evaluate the effect of framework internal
design changes on the mechanical properties of cobalt-chromium (Co-Cr) specimens manufactured
by using direct metal laser sintering (DMLS).
Material and methods
Dumbbell-shaped test specimens were designed as per the International Organization
for Standardization (ISO) 22674(E) standard by using a 3-dimensional software program.
A total of 70 dumbbell-shaped specimens were prepared by using Co-Cr alloy powder
and DMLS (n=10). The control group specimens were solid with the internal completely
filled. For the test groups, the internal design of the dumbbell-shaped specimens
was modified. Leaving the outer shell thickness of the specimens at 0.5 mm for all
test groups, 6 different internal designs were created, and the specimens were weighed.
The tensile strength test was used to evaluate the mean peak strength, elastic modulus,
and percentage elongation of the specimens. One-way ANOVA followed by the Dunnett
T3 test was used for statistical analysis (α=.05).
Results
A statistically significant difference was found among the groups in terms of bar
weight and peak strength (P<.05). The highest values were observed in the control group for all evaluated parameters
(mean ±standard deviation bar weight: 1321.3 ±36.6 mg, peak strength: 1045 ±36.7 MPa,
elastic modulus: 284.2 ±71.9 GPa, and elongation: 28.7 ±7%). However, no statistically
significant difference was observed for elastic modulus or percentage of elongation
(P>.05).
Conclusions
Decreasing the weight of the frameworks by changing the internal design of the specimens
also decreased the peak strength. However, it did not affect the elastic modulus or
the percentage of elongation.
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Publication history
Published online: July 19, 2021
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© 2021 by the Editorial Council for the Journal of Prosthetic Dentistry.
