The popularity of body piercing in today’s generation of orthodontic aged patients can mean that many of these patients may have already been sensitized to nickel by the time they see an orthodontist. Though, body piercing is not the subject of this article, it must be noted that that much of the metal used in jewelry contains nickel. You might ask, “what does nickel have to do with orthodontics?” Nickel is a metallic element used in many of the “high tech”, ultra-flexible wires, auxiliaries, and stainless steel appliances used in orthodontic practice today, including the braces themselves. Nickel is known to cause more cases of allergic contact dermatitis than all other metals combined. Most cases of nickel contact dermatitis are the result of direct contact from jewelry, clothes, watches, and glasses. Nickel is present in a large number of commonly used objects and can therefore cause contact dermatitis.
There has been a lot of research done on nickel hypersensitivity over the years. A Recent study in the American Journal of Orthodontics & Dentofacial Orthopedics set out to determine the prevalence of nickel hypersensitivity in orthodontic patients and compare it with the prevalence in the general population. A meta-analysis was performed on all previous valid studies to come up with a consensus view or recommendation.
How Does Nickel Cause Allergic Reactions?
Allergic reactions occur when the immune system reacts adversely to a foreign substance (antigen). Nickel induces a contact dermatitis, which is a Type IV delayed hypersensitivity immune response. There are 2 phases to this process. The sensitization phase occurs the instant the allergen (nickel) enters the body and causes a response. The elicitation phase occurs after the body is re-exposed to the antigen (nickel) a second time which causes the appearance of the full clinical manifestations. The initial exposure usually does not elicit symptoms, but subsequent contact with the antigen is usually enough to cause a more visible reaction.
Occurrence of Nickel Allergy: Who Is At Risk? What are the Symptoms?
The percentage of nickel in orthodontic appliances ranges from 8% (in stainless steel) to more than 50% (in nickel-titanium alloys). Estimates are that 4.5% to 28.5% of the total population are sensitized to nickel. Nickel hypersensitivity is more prevalent in females than in males by a factor of 10 to 1. This disproportionate hypersensitivity in females is thought to be related to their more frequent exposure to and contact with detergents, jewelry, earrings, and other metal objects such as watches, metal buttons, and buckles. For males, nickel hypersensitivity is related more to occupational exposure for example in industries where nickel is used as a raw material.
Another study reported that oral contact with nickel in normal, non-sensitized individuals may actually cause those individuals to become more resistant to nickel allergy.Sensitization to nickel is thought to be increased by mechanical irritation, skin maceration, or oral mucosal injury, all of which can occur in orthodontic practice.
Symptoms of nickel allergy include development of an allergic dermatitis and/or lesions of contact stomatitis which can be highly variable in nature and at times barely visible. Itching is not usually a common symptom and outside the mouth reactions (most commonly associated with headgear wear) are more common than inside the mouth reactions.
Diagnosis of Nickel Allergy
Nickel hypersensitivity induced contact dermatitis is confirmed through the use of a patch test in which small amounts of allergens are applied to the skin for a period of time. The dermatologist then measures the intensity of the skin’s reaction. A patch test score of +4 (the most severe of reactions) is characterized by the presence of erythema, edema, papules, and vesicles at the test site while a score of +2 presents in only erythema which is a much less intense allergic response. An erythematous allergic reaction is depicted below.
Correct diagnosis of nickel hypersensitivity is important. The following patient medical history would suggest a diagnosis of nickel allergy:
- a previous allergic response after wearing earrings or other metal item
- appearance of allergy symptoms following insertion of orthodontic components containing nickel
- extra-oral (outside the mouth) rash adjacent to headgear arms
It is very important to eliminate lesions associated with other causes:
- herpetic stomatitis
- ulcers due to mechanical irritation
- allergies to other materials such as acrylic
Recommendations For Nickel Sensitive Patients
As mentioned previously, many orthodontic components contain nickel alloys. Stainless steel contains approximately 8% nickel, while nickel titanium archwires contain approximately 50% or more nickel. It is important to note that most research has determined that all intra-oral orthodontic components made of stainless steel are safe to use in nickel hypersensitive patients because the molecular structure of stainless steel prevents the release of nickel and renders it unreactive. However, a nickel-free alternative to stainless steel brackets are available in the following forms:
- ceramic brackets
- polycarbonate or plastic brackets
- titanium brackets
- gold-plated brackets
Stainless steel orthodontic archwires are also considered safe in nickel sensitive patients. On the other hand, many high technology ultra-flexible nickel-titanium wires used in orthodontics today should be avoided in nickel sensitive patients. Alternate wires such as twist-o-flex, TMA, pure titanium, and gold-plated can be used without risk.
If a patient experiences a positive nickel sensitivity (positive patch test) reaction during orthodontic treatment it is recommended that all intraoral and/or extraoral appliances (braces) containing nickel be removed until the adverse reaction subsides. Once the lesions have healed, nickel-free appliances can be placed.
The popularity of body piercing in the teenage population will no doubt cause the sensitization of more orthodontic aged patients to the effects of nickel allergy in the coming years. Severe intra-oral reactions of nickel allergy are very rare, however, extra-oral reactions are more common. In the final analysis, research has concluded that orthodontic treatment is not associated with an increased occurrence of nickel sensitivity unless patients had his or her ears pierced.