Abstract
Cobalt-chromium (Co-Cr) alloy is a widely used base material for dental fixed prostheses. These restorations can be produced through casting technique, subtractive or additive manufacturing technologies. However, limited information is available regarding the influence of manufacturing techniques on the properties of Co-Cr alloy since most studies used different chemical compositions of Co-Cr alloy for different manufacturing methods. This study compares the mechanical properties, metal-ceramic bond strength, and microstructures of specimens produced by casting, milling, and selective laser melting (SLM) from one single Co-Cr alloy composition. The mechanical properties of the alloy were investigated by tensile and Vickers hardness tests, and metal-ceramic bond strength was determined by three-point bending. Scanning electron microscopy (SEM) with backscattered electron (BSE) images and optical microphotographs were used to analyze the surface microstructures. Compared with the casting and milling techniques, SLM Co-Cr alloy specimens indicated enhanced mechanical properties and comparable metal-ceramic bond strength. Besides, the microstructures of the SLM specimens showed finer grains with more second phase particles than the casting and milling specimens. The results of our study indicate that SLM might be superior to traditional techniques for the manufacturing of fixed dental restorations.
Highlights
Metal-ceramic prostheses, which are known as the porcelain-fused-to-metal (PFM) restorations, have been widely used in fixed dental prosthodontics because of the proper mechanical and aesthetic properties [1,2]
Computer-aided design and computer-aided manufacturing (CAD-CAM) technology has been introduced to fabricate the substrates. This technology can be divided into two main categories: Subtractive manufacturing processes like milling, and additive manufacturing processes like selective laser melting (SLM)
The SLM group showed the highest Ra value of all the three groups (p < 0.05), while there was no statistical difference between the casting and milling groups
Summary
Metal-ceramic prostheses, which are known as the porcelain-fused-to-metal (PFM) restorations, have been widely used in fixed dental prosthodontics because of the proper mechanical and aesthetic properties [1,2]. Co-Cr substrates are fabricated by the lost-wax casting technique, which is still the dominant method in dental metal processing. This technique requires a lot of time and certain skills for dental technicians and often results in pores and defects in the interior of the alloy [5,6]. Computer-aided design and computer-aided manufacturing (CAD-CAM) technology has been introduced to fabricate the substrates. This technology can be divided into two main categories: Subtractive manufacturing processes like milling, and additive manufacturing processes like selective laser melting (SLM). Milling can reduce flaws and pores which may be caused by the casting process because the Co-Cr blanks are made under high industrial standards, and the sample precision is related to the cutting performance [7]
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