Surface Micromorphology, Ion Release and Resistance to Corrosion of Orthodontic Wires Aesthetic Coating Subject to Degradation

• Published in: Journal of bio- and tribo-corrosion Vol. 8; no. 1
• Main Authors: de Amorim, Milena Carolina, da Rocha Gomes, Suelen, da Silva, Brunela Pereira, Aoki, Idalina Vieira, Basting, Roberta Tarkany
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.03.2022; Springer Nature B.V
• Subjects: Biomaterials; Chemical analysis; Chemical elements; Chemistry and Materials Science; Coating; Coatings; Corrosion; Corrosion and Coatings; Corrosion and Tribocorrosion in Dentistry; Corrosion resistance; Degradation; Electrochemical impedance spectroscopy; Electrode polarization; Emission analysis; Epoxy resins; Materials Science; Nickel; Nickel base alloys; Open circuit voltage; Optical emission spectroscopy; Orthodontics; Polarization; Rhodium; Saliva; Scanning electron microscopy; Scientific imaging; Solid Mechanics; Spectrometry; Spectroscopy; Surface analysis (chemical); Titanium; Titanium alloys; Tribology; Wire; Corrosion resistance; Electrochemical test; Artificial saliva solution; Orthodontic wires; Corrosion; Nitinol; Surface micromorphology
• DOI: 10.1007/s40735-021-00621-5
• ISSN: 2198-4220

This study aimed to conduct an in vitro analysis of orthodontic aesthetic wires submitted to degradation in artificial saliva solution, regarding surface micromorphology, chemical elements released, and corrosion resistance. Nickel-titanium 0.018-inch wire segments (GAC) were tested according to the following groups ( n  = 5): wires with aesthetic epoxy resin coating (E), wires with aesthetic thermoactivated rhodium coating (R), aesthetic uncoated nickel-titanium wires, and aesthetic thermoactivated uncoated nickel-titanium wires. All the wires were subjected to degradation for 30 days in artificial saliva solution (pH 5.8) at 37 °C. Surface analysis was performed before and after degradation of the wires, using a scanning electron microscope (900×). Chemical analyses using OES (optical emission spectrometry) were performed on the saliva solution used to store the wires. Corrosion resistance analyses were performed using electrochemical tests: open circuit potential monitored for 2 h, electrochemical impedance spectroscopy (EIS), and potentiodynamic cyclic polarization. Maps of chemical elements contained in the wire compositions after conducting electrochemical tests were obtained using energy-dispersive X-ray spectrometry. Kruskal Wallis and Dunn’s nonparametric tests ( α  = 5%) were applied for EIS, cyclic polarization and OES analysis. Chemical analysis indicated that E had lower detectable nickel release than the other wires ( p  < 0.05). EIS analysis confirmed that E provided the nickel-titanium alloy with greater protection ( p  < 0.05). The cyclic polarization test revealed that E presented the highest corrosion resistance, and that R showed the lowest resistance ( p  < 0.05). All the wires showed surfaces with increased irregularities after degradation challenge. E had released less nickel in saliva, and showed greater resistance to corrosion.