Corrosion resistance of a new Ti-12.5Zr-3Nb-2.5Sn alloy / 中华口腔医学杂志

<p><b>OBJECTIVE</b>to evaluate the corrosion resistance of a new titanium alloy for dental restoration in artificial saliva.</p><p><b>METHODS</b>in simulated oral environment, the electrochemical behavior of a new titanium alloy (Ti-12.5Zr-3Nb-2.5Sn) for dental restoration based on the d-electron alloy design method with high elastic modulus, high mechanical and good biological safety properties was investigated together with that of Ti-6Al-4V and TA2 as control groups. The anodic polarization curve and polarization resistance of these alloys were analyzed and the element release of Ti-12.5Zr-3Nb-2.5Sn and Ti-6Al-4V alloy after immersion in artificial saliva for 1, 2, 3, 5, 7, 15 d were measured.</p><p><b>RESULTS</b>polarization curve indicated that Ti-6Al-4V alloy had lower breakdown potential (0.8 V) than Ti-12.5Zr-3Nb-2.5Sn alloy did (> 2.5 V). Ti-6Al-4V alloy showed higher passivation current density (1.45 × 10(-4) - 1.09 × 10(-3) A/cm(2)) than Ti-12.5Zr-3Nb-2.5Sn alloy (3.32 × 10(-6) - 3.46 × 10(-5) A/cm(2)) and TA2(5.03 × 10(-6) - 2.65 × 10(-5) A/cm(2)) did. Polarization resistance results showed that polarization resistance volume of TA2, Ti-12.5Zr-3Nb-2.5Sn alloy and Ti-6Al-4V alloy were 371.0, 252.0, and 60.1 kΩ×cm(2) respectively. With the increasing of dipping time in artificial saliva, the ion release of Ti-12.5Zr-3Nb-2.5Sn alloy and Ti-6Al-4V alloy increased to different degrees. Ti-6Al-4V alloy always showed more ion release than Ti-12.5Zr-3Nb-2.5Sn alloy did in the experiment.</p><p><b>CONCLUSIONS</b>data from this study indicated that Ti-12.5Zr-3Nb-2.5Sn alloy, as a dental restoration material, had good corrosion resistance in artificial saliva.</p>

Effect of different heat treatment on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of heat treatment and porcelain-fused-to-metal (PFM) processing on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys.</p><p><b>METHODS</b>Samples of CoCr-NiCr dissimilar alloys with 0.5 mm thickness were laser-welded single-side under the setting parameters of 280 V, 10 ms pulse duration. After being welded, samples were randomly assigned to three groups, 10 each. Group1 and 2 received heat treatment and PFM processing, respectively. Group 3 was control group without any treatment. Tensile strength, microstructure and element distribution of samples in the three groups were tested and observed using tensile test, metallographic examinations, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) analysis.</p><p><b>RESULTS</b>After heat treatment and PFM processing, tensile strength of the samples were (537.15 +/- 43.91) MPa and (534.58 +/- 48.47) MPa respectively, and elongation rates in Group 1 and 2 were (7.65 +/- 0.73)% and (7.40 +/- 0.45)%. Ductile structure can be found on tensile fracture surface of samples and it was more obvious in heat treatment group than in PFM group. The results of EDS analysis indicated that certain CoCr alloy diffused towards fusion zone and NiCr side after heat treatment and PFM processing. Compared with PFM processing group, the diffusion in the heat treatment group was more obvious.</p><p><b>CONCLUSIONS</b>Heat treatment and PFM processing can improve the mechanical properties and microstructure of welded CoCr-NiCr dissimilar alloy to a certain degree. The improvements are more obvious with heat treatment than with porcelain treatment.</p>