Citation: Fu, W.; Liu, S.; Jiao, J.; Xie,
Z.; Huang, X.; Lu, Y.; Liu, H.; Hu, S.;
Zuo, E.; Kou, N.; et al. Wear
Resistance and Biocompatibility of
Co-Cr Dental Alloys Fabricated with
CAST and SLM Techniques. Materials
2022, 15, 3263. https://doi.org/
10.3390/ma15093263
Academic Editor: Javier Gil
Received: 6 April 2022
Accepted: 28 April 2022
Published: 2 May 2022
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Article
Wear Resistance and Biocompatibility of Co-Cr Dental Alloys
Fabricated with CAST and SLM Techniques
Wenqi Fu
1,2
, Shuang Liu
1,2,†
, Jun Jiao
1,2,†
, Zhiwen Xie
3
, Xinfang Huang
3
, Yun Lu
1,2
, Huiying Liu
1,2
,
Shuhai Hu
1,2
, Enjun Zuo
1,2
, Ni Kou
1,2,
* and Guowu Ma
1,2,
*
1
Department of Oral Prosthodontics, School of Stomatology, Dalian Medical University, Lvshun South Road,
Dalian 116044, China; fwq0369@163.com (W.F.); hdllsphsss@163.com (S.L.); junjunjiaojun@126.com (J.J.);
lyyida2009@126.com (Y.L.); lhy04512000@163.com (H.L.); shuhaihu4141@aliyun.com (S.H.);
zuoej@163.com (E.Z.)
2
Academician Laboratory of Immune and Oral Development & Regeneration, Dalian Medical University,
Lvshun South Road, Dalian 116044, China
3
School of Mechanical Engineering and Automation, University of Science and Technology Liaoning,
Anshan 114051, China; xzwustl@126.com (Z.X.); xfgg527@163.com (X.H.)
* Correspondence: kouni1984@163.com (N.K.); Mgw64024@163.com (G.M.)
† These authors contributed equally to this work.
Abstract:
Cobalt–chromium (Co-Cr) alloys have been widely used as dental-restoration materials
for many years. This study sought to investigate whether selective laser melting (SLM) is a more
appropriate process than traditional casting (CAST) for fabricating dental Co-Cr alloys. Metallurgical
microscopy, X-ray photoelectron spectroscopy (XPS), Vickers hardness and nanoindentation tests, and
friction and wear tests were used to evaluate the microstructure, surface compositions, mechanical
properties, and wear resistance, respectively. Additionally, the biocompatibilities and cell adhesion of
the alloys were evaluated with L-929 fibroblasts via CCK-8 assay, Live/Dead staining, flow cytometric
analysis, scanning electron microscopy (SEM) observation and real-time PCR (RT-PCR) assay. The
XPS results showed that the two alloys were all mainly comprised of Co, Cr, and O. The hardness in
the CAST group equaled 7.15
±
0.48 GPa, while in the SLM group, it equaled 9.06
±
0.49 GPa. The
friction coefficient of SLM alloys remained at approximately 0.46, but the CAST specimens fluctuated
significantly. SLM alloys exhibited shallower wear scars and less wear debris compared with CAST
alloys, simultaneously. Additionally, there were higher survival and expression of cell-adhesion-
related genes on SLM alloys of L-929 cells, which meant that the deleterious effect on L-929 cells was
significantly reduced compared with that for the CAST alloys. Overall, the wear resistances and
biocompatibilities of the Co-Cr dental alloys were dramatically affected by the fabrication technique.
The SLM technique is advantageous over the CAST technique for fabricating Co-Cr dental alloys.
Keywords:
dental restoration wear; biocompatible; casting technics; cobalt–chromium alloys;
selective laser melting
1. Introduction
Co-Cr alloys have been increasingly used for dental restorations owing to their ex-
cellent mechanical properties, corrosion resistance, and metal–ceramic combination [
1
].
However, the flaws, porosity, and costs arising from the complex steps of the traditional
lost-wax casting technique seriously limit its applicability [
2
–
5
]. Simplification of the pro-
cedures can mitigate these errors, along with cost of improving the restoration quality.
Computer-aided design/computer-aided manufacturing (CAD/CAM) provides advanced
routes for alloy processing as an alternative to the CAST [
6
]. The impression-taking pro-
cedure can be avoided via the development of direct oral-scanning devices, improving
the fabrication-time efficiency and the precision of the dental restorations. Depending
on the processing method, it can be divided into subtractive and additive processes. The
Materials 2022, 15, 3263. https://doi.org/10.3390/ma15093263 https://www.mdpi.com/journal/materials
