The question of whether the metal in braces can rust is a common concern, given that these appliances are placed in the constantly moist environment of the mouth. Rust is the specific term for the corrosion of iron, producing reddish-brown iron oxide. Modern orthodontic braces, including the brackets and wires, are engineered specifically to prevent this degradation. Because contemporary orthodontic materials either contain no iron or are highly alloyed with elements that shield the iron, the specific chemical process of rusting simply does not occur.
The Specialized Metals Used in Orthodontics
The materials chosen for orthodontic appliances result from decades of biomedical engineering focused on strength, flexibility, and biocompatibility. The brackets attached to the teeth are most commonly made from medical-grade stainless steel. This alloy is composed of iron blended with elements like chromium and nickel, which fundamentally change its chemical properties.
Archwires, which provide the force necessary for tooth movement, often utilize specialized materials to deliver consistent pressure. A popular choice is the nickel-titanium (NiTi) alloy, known for its superelasticity and shape memory properties. Titanium alloys are also used for patients with nickel sensitivities. These materials are strong, lightweight, and highly resistant to environmental breakdown in the challenging oral environment.
The Science of Corrosion Resistance
The ability of these metals to resist corrosion in the mouth relies on a phenomenon called passivation, which creates a protective surface layer. Stainless steel, in particular, contains a minimum of 10.5% chromium, which reacts instantly with oxygen to form a microscopically thin film of chromium oxide. This passive layer acts as an impenetrable barrier, chemically sealing the underlying metal from saliva, food acids, and other corrosive agents.
If this passive layer is scratched or damaged, it possesses a self-healing property, reforming immediately upon contact with oxygen in the air or saliva. Nickel-titanium wires also rely on passivation, forming a similar protective layer based on titanium dioxide. This mechanism prevents the continuous oxidative process that characterizes rust or general corrosion. This ensures the structural integrity of the appliance throughout the treatment period, despite the mouth’s moist, warm environment and varying pH levels.
What People Mistake for Rust
When patients notice a brownish or orange discoloration on their braces, they understandably assume it is rust, but the cause is almost always external. One of the most common culprits is the accumulation of dental plaque and its hardened form, tartar, around the brackets and wires. Plaque is a sticky bacterial film that can become stained by pigmented substances, taking on a color that falsely suggests metal degradation.
The tiny elastic ligatures or rubber bands used to hold the archwire to the brackets are also highly susceptible to staining. Highly pigmented foods and drinks such as coffee, dark sodas, red wine, or tomato-based sauces can quickly transfer color to these porous elastic components. This staining is purely cosmetic and does not affect the function or structural strength of the metal appliance itself.
A dulling of the metal surface, known as tarnish, can sometimes occur. Tarnish is a minor surface change that is not a structural failure of the material.
Maintaining Brace Integrity and Appearance
Preventing the staining and buildup that is often mistaken for rust requires consistent, meticulous oral hygiene practices. Brushing should be performed after every meal using a soft-bristled toothbrush to carefully clean all surfaces of the teeth, brackets, and wires. Specialized tools, such as interdental brushes or floss threaders, are necessary to navigate the small spaces beneath the archwires and between brackets where food particles become trapped.
Dietary choices affect the appearance of the appliances, especially the elastic ties. Limiting the consumption of highly acidic beverages and deeply colored foods reduces the potential for visible staining. Regular appointments with the orthodontist and general dentist are also important, as professional cleanings remove hardened tartar and the orthodontic team replaces the elastic ligatures at every adjustment visit.