The possibility of the formation of hydrofluoric acid by the reaction of fluoride with acetic acid seems natural in the oral cavity. The effect of an acidic fluoride solution on NiTi wires was investigated by testing microhardness and color changes on wires. For aesthetic reasons, the color change on wires was also evaluated. Wires were immersed in four different test solutions for 1 or 3 days. As-received wires were used as a reference. After immersion for 3 days, the microhardness of the tested wires increased 1.8% to 10.4% compared to that of their as-received state. Wires immersed in a higher NaF concentration, lower pH solution with longer immersion yielded a more corroded surface than those of the counter cases. Wires showed a different color after immersion. However, after 3 days in solutions of pH 4, wires showed an appreciable color change regardless of the products. In test solutions, 3M wires showed the highest volumetric and percentage (0.59 for 0.05%; 1.19 for 0.2% solution) weight loss and G&H wires showed the least volumetric and percentage (0.43 for 0.05%; 1.05 for 0.2% solution) weight loss among tested wires. In pH 6 solutions, wires lost weight and were under the detection limit of the testing machine.
The Ag–Pd–Cu–Pt–Zn alloy was studied in order to elucidate the age hardening behaviour, phase transformation and changes in microstructure and element distribution during the aging process. The grain interior precipitation of the Cu rich phase from the Ag rich α1 matrix caused an apparent increase in hardness, and the formation and expansion of the Cu rich entanglement structures decreased the hardness. The phase transformation of the Cu–Pd rich α2 phase occurred during softening in the later stage of the aging process, which resulted in the retardation of further softening. Pt was concentrated in the Cu–Pd-rich α2 particle-like structures, and Zn was exclusively concentrated in the CuPd β particle-like structures at approximately four times its concentration in the original alloy composition. The Cu–Pd rich α2 and CuPd β phases, which contained large amounts of Cu, constituted the particle-like structures of various sizes without an apparent contribution to the age hardenability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.