Nanotopography Evaluation of NiTi Alloy Exposed to Artificial Saliva and Different Mouthwashes

Abstract

Nitinol (NiTi) alloy is a widely used material for the production of orthodontic archwires. Its corrosion behavior in conditions that exist in the oral cavity still remains a great characterization challenge. The motivation behind this work is to reveal the influence of commercially available mouthwashes on NiTi orthodontic archwires by performing non-electrochemical corrosion tests and quantifying the changes in the nanotopography of commercially available NiTi orthodontic wires. In this study, we examined the behavior of NiTi alloy archwires exposed for 21.5 days to different corrosive media: artificial saliva, Eludril®, Aquafresh®, and Listerine®. The corrosion was characterized by contact mode atomic force microscopy (AFM) before and after the corrosion tests. A novel analysis methodology was developed to obtain insight into locations of material gain or material loss based on standard surface roughness parameters Sa, Sdr, Ssk, and S10z. The developed methodology revealed that fluoride-containing mouthwashes (Aquafresh® and Listerine®) dominantly cause material loss, while chloride-containing mouthwash (Eludril®) can cause both material loss and material gain. The sample exposed to artificial saliva did not display significant changes in any parameter.

Cytotoxicity of Metal Ions Released from NiTi and Stainless Steel Orthodontic Appliances, Part 1: Surface Morphology and Ion Release Variations

“…Overall, the effect of immersion in artificial saliva on morphological changes on NiTi surface was manifested primarily through the increased number of salt deposits. This result agrees well with the study of Bobić et al [51], where no significant changes were observed for NiTi surface roughness after 21 days of immersion.…”

“…The surface roughness is reported as the arithmetic average height parameter, S a , a commonly used parameter which, in general, provides a good description of height variations [70]. However, for examining the corrosion effects on larger areas (note that the results are reported for a 256 × 256 µm area), the S a parameter was found to be insufficient [51]; hence, the S dr parameter was also used. The S dr parameter denotes the developed interfacial area ratio, i.e., the percentage of additional surface area contributed by the texture as compared to an ideal plane the size of the measurement region.…”