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
• ISSN: 2198-4220; 2198-4239
• DOI: 10.1007/s40735-021-00621-5

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.