Evaluation of physical and mechanical properties of metal substructures soldered by different methods

Non-noble metal alloys are the most commonly used metal alloys in removable and fixed prosthetic restorations. Cobalt-chromium (Co-Cr) alloys are often preferred due to cheapness, availability, and sufficient strength. The aim of this study is to determine the tensile strengths of Co-Cr infrastructures fabricated by different methods after conventional and laser soldering. For this purpose, Co-Cr metal alloys were fabricated with conventional casting, laser sintering and computer aided design and computer aided manufacturing (CAD/CAM) methods. 24 samples (2x4x25cm) were fabricated for each group. Eight of the samples from each group consisted of control samples, eight of them were soldered by conventional method and eight of them were laser soldered. All samples were subjected to tensile strength testing. Tensile strengths in non-soldered samples were measured and the higher results were found in the laser sintering, CAD/CAM and conventional casting groups, respectively. The highest tensile strength in casted samples was obtained in the laser soldered samples. The highest tensile strength of the samples fabricated by laser sintering and CAD / CAM were obtained in non-soldered samples. Conventional soldering procedure reduced tensile strength in all samples, and the maximum reduction was found in the samples fabricated by laser sintering. Laser soldering increased the tensile strength in casted samples while decreasing the strength of laser sintering and CAD / CAM samples. The physical properties of the metal after the soldering process may vary depending on the fabrication method of the metal to be soldered. Particularly, the non-soldered samples have lower tensile strength than the soldered samples, especially since laser sintering provides a more intensive metal structure. As a conclusion, tensile strength of all samples soldered with the exception of samples fabricated by conventional casting and laser-soldered was found to be lower than those without soldering. Laser soldering affected the tensile strength of the alloy lower than gas soldering. Keywords: CAD/CAM, Casting, Laser sintering, Laser soldering, Gas soldering