Abstract
Statement of problem
Sintering-based computer-aided metal manufacturing strategies have been proposed as
an alternative to hard metal milling. While these fabrication methods have been evaluated
in terms of marginal and internal discrepancies and bond strength to porcelain, limited
information on metal frameworks is available regarding their flexural yield strength.
Purpose
The purpose of this in vitro study was to evaluate the flexural yield strength of
3-unit cobalt-chromium (Co-Cr) metal frameworks fabricated by hard metal milling (HMM),
presintered soft metal milling (PSMM), and direct metal laser melting (DMLM) with
25-μm and 50-μm layer thicknesses.
Material and methods
Three-unit master metal die models were prepared. A total of 40 metal frameworks (n=10)
were fabricated by using HMM (group HM), PSMM (group PSM), and DMLM with 25-μm (group
LM25) and 50-μm layer thicknesses (group LM50). Metal frameworks were cemented to
the master die and then subjected to a 3-point bend test. The flexural yield force
was used to calculate the flexural yield strength. The data were statistically analyzed
(α=.05). One metal framework from each group was evaluated with scanning electron
microscopy for microstructural analysis.
Results
The group LM50 exhibited the lowest significant (P<.001) flexural yield strength values. The group HM exhibited higher flexural yield
strength values than the other groups. No significant difference was found between
the groups LM25 and PSM (P=.954) or between the groups PSM and HM (P=.111).
Conclusions
The fabrication method significantly affected the flexural yield strength of metal
frameworks. Metal frameworks fabricated by DMLM with a 50-μm layer thickness exhibited
considerably lower flexural yield strength values.
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Article info
Publication history
Published online: May 05, 2022
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© 2022 by the Editorial Council for The Journal of Prosthetic Dentistry.
