Abstract
Statement of problem
Selective laser melting (SLM) additive manufacturing (AM) technology is a current
option to fabricate cobalt-chromium (Co-Cr) metal frameworks for dental prostheses.
However, the Co-Cr alloy composition, surface roughness, and ceramic bond strength
values that SLM metals can obtain are not well-defined.
Purpose
The purpose of this in vitro study was to compare the chemical composition, surface
roughness, and ceramic shear bond strength of the milled and SLM Co-Cr dental alloys.
Material and methods
A total of 50 disks of 5 mm in diameter and 1 mm in thickness were fabricated by using
subtractive (control group) and AM with each of following SLM providers: SLM-1 (EOS),
SLM-2 (3D systems), and SLM-3 (Concept Laser). The milled disks were airborne-particle
abraded with 100-μm aluminum oxide particles. All the specimens were cleaned before
surface roughness (Ra), weight (Wt%), and atomic (At%) percentages were analyzed.
Three-dimensional profilometry was used to analyze the topographical properties of
the surface parameters Ra (mean surface roughness). The chemical composition of Co-Cr
alloy specimens was determined by using energy dispersive X-ray (EDAX) elemental analysis
in a scanning electron microscope (SEM). Thereafter, the specimens were bonded to
a ceramic (Dentine A3 and Enamel S-59; Creation CC) interface. Specimens were stored
for 24 hours at 23 °C. The bond strength of the SLM-ceramic interface was measured
by using the macroshear test (SBT) method (n=10). Adhesion tests were performed in
a universal testing machine (1 mm/min). The Shapiro-Wilk test revealed that the chemical
composition data were not normally distributed. Therefore, the atomic (At%) and weight
percentages (Wt%) were analyzed by using the Kruskal-Wallis test, followed by pairwise
Mann-Whitney U tests between the control and AM groups (AM-1 to AM-4). However, the
Shapiro-Wilk test revealed that the surface roughness (Ra) and ceramic bond strength
data were normally distributed. Therefore, data were analyzed by using 1-way ANOVA,
followed by the post hoc Sidak test (α=.05).
Results
Significant differences were obtained in Wt%, At%, and Ra values among the Co-Cr alloys
evaluated (P<.05). Furthermore, the control group revealed significantly lower mean ±standard
deviation Ra values (0.79 ±0.11 μm), followed by AM-3 (1.57 ±0.15 μm), AM-2 (1.80
±0.43 μm), AM-1 (2.43 ±0.34 μm), and AM-4 (2.84 ±0.27 μm). However, no significant
differences were obtained in the metal-ceramic shear bond strength among the different
groups evaluated, ranging from mean ±standard deviation 75.77 ±11.92 MPa to 83.65
±12.21 MPa.
Conclusions
Co-Cr dental alloys demonstrated a significant difference in their chemical compositions.
Subtractive and additive manufacturing procedures demonstrated a significant influence
on the surface roughness of the Co-Cr alloy specimens. However, the metal-ceramic
shear bond strength of Co-Cr alloys was found to be independent of the manufacturing
process.
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Article info
Publication history
Published online: May 25, 2020
Identification
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© 2020 by the Editorial Council for The Journal of Prosthetic Dentistry.
