# Low-Friction and Corrosion-Resistant Orthodontic Stainless Steel Archwires with Functional Carbon Films

## TL;DR

This paper introduces a new method to coat orthodontic wires with carbon films to reduce corrosion and friction, even when exposed to fluoride solutions.

## Contribution

The study presents a novel plasma sputtering method to fabricate corrosion-resistant and low-friction carbon films on orthodontic stainless steel archwires.

## Key findings

- Carbon films deposited at +50 V for 80 min showed exceptional corrosion resistance in fluoride solutions.
- The films exhibited low friction and wear rates after exposure to fluoride toothpaste mixed solutions.
- Amorphous and graphene-like carbon films were identified based on deposition parameters.

## Abstract

To mitigate the adverse effects of immersion in fluoride-containing solutions on the surface corrosion of orthodontic stainless steel archwires, carbon films were fabricated on these archwires under various deposition times and substrate bias voltages using a self-designed plasma sputtering system. Structural analysis revealed that the carbon films deposited at lower substrate bias voltages were classified as amorphous carbon films, whereas those fabricated at higher substrate bias voltages were identified as graphene nanocrystalline carbon films. Particularly, immersion tests and electrochemical experiments demonstrated that carbon film prepared at a substrate bias voltage of +50 V for 80 min exhibited exceptional corrosion resistance. Furthermore, a low friction coefficient and low wear rate were obtained even after soaking in a fluoride toothpaste mixed solution. The mechanisms underlying the corrosion resistance and friction properties of these superior carbon films were thoroughly investigated. This study provides valuable insights into the application of carbon film for reducing friction and wear while enhancing corrosion resistance, thus promoting their practical clinical applications in coated orthodontic stainless steel archwires.