Properties of titanium–silver alloys for dental application

Abstract

The purpose of this study was to develop titanium-silver alloys with biocompatibility, high corrosion resistance, and low ion-release rate, and to evaluate the electrochemical properties of titanium-silver alloys in artificial saliva. Titanium-silver alloys with silver contents ranging from 0 to 4.5 at % in steps of 0.5 at % were designed. The alloys were arc melted, homogenized at 950 degrees C for 72 h, hot rolled to 2 mm in thickness, and finally solution heat treated at 950 degrees C for 1 h and quenched in water. Chemical compositions, phases, hardnesses, electrochemical properties, and the cytotoxicity of the alloys were investigated. The purity of titanium-silver alloys was maintained above 99.9%, because few impurities were introduced through their manufacture. In the case of alloys containing silver in the range 2.0-4.0 at %, the formation of an acicular alpha phase was observed inside the beta phase. The acicular phase got thinner with increasing amounts of silver. This means that silver is a beta-phase stabilizing element in titanium-silver alloys. The hardness value tended to rise with increasing silver content and increased largely over 3.5 at %, and the increase of the hardness value versus pure titanium was about 33%. It is believed that the substantial increases in hardness was due to the effects of solid solution strengthening and of alpha-beta phase transition. Moreover, titanium-silver alloys had higher corrosion resistances than pure titanium. These results mean that silver additions to titanium can improve alloy corrosion resistance. Passive current densities in the potentiodynamic polarization curves were dependent on the chemical compositions of the titanium-silver alloys. However, they did not show a linear relationship with respect to silver contents. Titanium-silver alloys did not show pitting corrosion in artificial saliva. It is believed that silver addition to titanium strengthened the passive film due to titanium dissolution induced by the different electromotive forces of titanium and silver. In the agar overlay test, the cytotoxicity of the titanium-silver alloys and of titanium were none or mild. In summary, titanium-silver alloys had higher mechanical properties and corrosion resistance than titanium, and toxicities that were similar to titanium. Therefore, it is recommended that titanium-silver alloys be adopted cautiously by the biomedical and dental fields.

Development of Ti‐Ag‐Fe ternary titanium alloy for dental application

“…After 7200 s immersion, the corrosion potentials of Ti-5Ag, Ti-5Ag-1Fe, Ti-5Ag-2.5Fe, and Ti-5Ag-5Fe alloys are À39 6 14 mV, À52 6 33 mV, À55 6 18 mV, and 69 6 22 mV, which are significantly higher (p < 0.05) than that of CP Ti (À121 6 39 mV). Similar results can be observed in Ti-Ag binary alloys [8][9][10] and Ti-Ag-Cu ternary alloys, 34 and it assumed thicker or more stable oxide films formed on TiAg based alloys. Figure 9 shows the typical potentiodynamic polarization plots for experimental alloys in different solutions.…”

“…1,2 However, the insufficient strength and poor wear resistance of unalloyed titanium (Ti) was often complained. 3,4 Because the properties of unalloyed titanium are not suitable for certain purposes, many titanium alloys, such as titanium-copper 3,[5][6][7] alloys, titanium-silver alloys, [6][7][8][9][10] titanium-hafnium alloys, 11,12 and titanium-zirconium alloys 13 have been developed for dental application, and their properties have been studied mainly to improve the strength and castability of pure titanium.…”

“…[6][7][8][9][10] The tensile strength and grindability of pure titanium could be improved by silver (Ag) addition. 6,8 It was reported that the tensile strength of Ti-20Ag alloy is 60% higher than that of pure titanium; moreover, the elongation is over 19%. 6 The grindability of titanium was also found to be improved by alloying with Ag element, especially at high speed grinding.…”

“…6 In our previous work, 10 the presence of 5 wt % Ag is found to be enough to raise the corrosion potential of the Ti-Ag system, Ti-5Ag alloy exhibited good passivation behavior in simulated body environment. Moreover, Oh et al 8 reported that Ti-Ag alloys (0-4.5 at %) exhibit little cytotoxicity to the mouse fibroblast cell line. However, the yield strength of Ti5Ag alloy is about 280 MPa, 6 which is still much lower than that of Ti-6Al-4V alloy (about 800 MPa).…”

Effect of Indium Content on the Microstructure, Mechanical Properties and Corrosion Behavior of Titanium Alloys

“…Several Ti-X binary alloys have been developed, such as Ti-Nb [5][6][7], Ti-Ag [8,9], Ti-Au [10], Ti-Hf [11], Ti-Mn [12], Ti-Cr [13,14], Ti-Mo [15], Ti-Sn [16], Ti-Zr [17][18][19], Ti-Ta [20,21], Ti-Co [22], Ti-Pd [23], Ti-Ge [24] and Ti-Cu [25] alloys. The mechanical properties of Ti alloys are influenced by their microstructure, which, in turn, depends on chemical composition and synthetic processing.…”