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Microstructure and mechanical properties of 3D-printed dental Co-Cr alloys, produced with the use of selective laser melting

Cherneva Sabina, Petrunov Vladimir, Petkov Vladimir, Bogdanov Vladimir, Simeonova Silviya

Acta of Bioengineering and Biomechanics

2023

Vol. 25, no. 2

29--40

The aim of present work was to investigate microstructure and mechanical properties of 3D printed by selective laser melting (SLM) Co-Cr alloys, intended for additive manufacturing in dentistry. Methods: A scanning electron microscope (SEM), equipped with an integrated Energy-Dispersive X-Ray Spectroscopy (EDS) system was used for investigation of the surface morphology and elemental composition of the 3D-printed Co-Cr sample. The X-ray structural analysis of the 3D-printed Co-Cr sample was made with a Bruker D8 Advance powder X-ray diffractometer. An atomic force microscopy (AFM) was used to investigate the surface topography of the sample. Tensile test, a three-point bending test and nanoindentation experiments were conducted for investigation of mechanical properties of the 3D-printed Co-Cr sample. The influence of two different strain rates (1 mm/min and 60 mm/min) on the flexural strength was investigated as well. Results: Higher values of indentation hardness (6.76 GPa), tensile strength (1016 MPa), yield strength (636.5 MPa) and flexural strength (1908 and 1891 MPa) of the Co-Cr alloys produced with the use of selective laser melting have been obtained, compared to cast Co-Cr and Cr-Ni alloys. It was found that increasing the strain rate from 1 mm/min to 60 mm/min caused a proportional decrease in recorded flexural strength of ~0.9%. Conclusions: The obtained results showed that the laser-sintered Co-Cr alloy can fully replace the cast Co-Cr alloy in dentistry, regarding its good mechanics properties as well as the high precision of the final product.

Investigation of mechanical and physicochemical properties of clinically retrieved titanium-niobium orthodontic archwires

Stoyanova-Ivanova Angelina, Cherneva Sabina, Petrunov Vladimir, Petrova Violeta, Ilievska Ivana, Mikli Valdek, Iankov Roumen

Acta of Bioengineering and Biomechanics

2020

Vol. 22, no. 1

31--39

Most of the orthodontic archwires used in the clinical practice nowadays contain nickel (Ni), however, many patients, especially kids, are allergic to Ni. One possible Ni-free alternative is the Titanium-Niobium (Ti-Nb) archwire. Unfortunately, there is not enough information about its mechanical properties in the literature, especially after clinical usage. Therefore, the aim of this work was to investigate and compare the mechanical properties, chemical composition, structure and morphology of as received and used in clinical practice Ti-Nb orthodontic archwires. Materials and methods: We investigated and compared as received and clinically retrieved after 4 and 6 weeks respectively Ti-Nb archwires with dimensions 0.43 × 0.64 mm (0.017 in. × 0.025 in.). The following methods were used: instrumented indentation testing (nanoindentation), X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Results: The nanoindentation investigations of as received and used Ti-Nb archwires revealed a decreasing in their indentation hardness with increased periods of use in the patient’s mouth. Moreover, an increasing of the concentration of Ti in the content of the TiNb alloy was associated with an increased period of use in the oral cavity. The SEM analysis showed changes in surface morphology with increasing the period of use of the archwires. Conclusions: The results showed that there are slight changes in the mechanical and physicochemical properties of the investigated wires after their use in the patient’s mouth. That is why we do not recommend them for recycling.