Abstract
Statement of problem
Laser sintering devices have been increasingly used to fabricate the metal frameworks
of metal–ceramic restorations. In the fabrication process, the sintering layer thickness
is an important parameter; however, information on how it may affect the flexural
strength of metal frameworks remains limited.
Purpose
The purpose of this in vitro study was to evaluate the flexural strength of 3-unit
and 4-unit cobalt-chromium (Co-Cr) metal frameworks laser sintered with 20-μm, 30-μm,
and 40-μm layer thicknesses.
Material and methods
Three-unit and 4-unit master metal die models with premolar and molar abutments were
prepared through direct metal laser sintering (DMLS). A total of 40 metal frameworks
(n=10 for each metal die model) were fabricated by the lost-wax technique (group C,
served as the control group) and through DMLS with 20-μm, 30-μm, and 40-μm layer thickness
(experimental groups LS20, LS30, and LS40, respectively). Each metal framework was
cemented to a master die with a polyvinyl siloxane impression material and then subjected
to a 3-point bend test at a crosshead speed of 1 mm/min. The yield force of each metal
framework was used to calculate the flexural strength. Data were statistically analyzed
by using 1-way ANOVA followed by a Tukey honestly significant difference (HSD) test
and an independent-samples t test (α=.05) The microstructure of the fracture surface was evaluated by scanning
electron microscopy.
Results
Group C reported the lowest mean flexural strength (P<.05), whereas group LS20 reported the highest mean flexural strength, although no
significant difference (P>.05) in flexural strength was observed among the DMLS groups. The 3-unit metal frameworks
exhibited a statistically significant higher mean flexural strength than the 4-unit
metal frameworks (P<.05).
Conclusions
The sintering layer thickness did not significantly affect the flexural strength of
the laser-sintered metal frameworks. However, the DMLS groups reported a higher mean
flexural strength than the cast group.
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Article info
Publication history
Published online: February 24, 2021
Footnotes
Supported by the Scientific and Technological Research Council of Turkey with the grant number of 119S066.
Identification
Copyright
© 2020 by the Editorial Council for the Journal of Prosthetic Dentistry.
