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Current Products and Practice

Nickel allergy and orthodontics

¹ Leeds Dental Institute, Leeds, UK
² Mayday Hospital, Surrey, UK

Gerry Rahilly, Orthodontic Department, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU, UK. Email: gerardrahilly{at}hotmail.com

	Abstract

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
Nickel is the most common metal to cause contact dermatitis in orthodontics. Nickel-containing metal alloys, such as nickel-titanium and stainless steel, are widely used in orthodontic appliances. Nickel-titanium alloys may have nickel content in excess of 50 per cent and can thus potentially release enough nickel in the oral environment to elicit manifestations of an allergic reaction. Stainless steel has a lower nickel content (8 per cent). However, because the nickel is bound in a crystal lattice it is not available to react. Stainless steel orthodontic components are therefore very unlikely to cause nickel hypersensitivity. This article discusses the diagnosis of nickel allergy in orthodontics and describes alternative products that are nickel free or have a very low nickel content, which would be appropriate to use in patients diagnosed with a nickel allergy.

Key words: Delayed hypersensitivity, nickel allergy, nickel-titanium, nickel-free

	Introduction

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
Dermatitis due to contact with nickel was first reported at the end of the nineteenth century among workers in the nickel plating industry and was recognized as an allergic response in 1925. This article discusses nickel allergy in orthodontics. After briefly discussing the biology of the reaction, we will explain the signs, symptoms and diagnosis of the condition. We will then discuss orthodontic appliance treatment options for patients with nickel allergy.

	Biology of the reaction

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
An allergic response is one in which certain components of the immune system react excessively to a foreign substance. Nickel elicits contact dermatitis, which is a Type IV delayed hypersensitivity immune response.¹ This process has two interrelated, distinct phases. A sensitization phase occurs from the moment the allergen enters the body, is recognized and a response occurs. The elicitation phase occurs after re-exposure to the allergen to the appearance of the full clinical reaction. There may have been no symptoms at the initial exposure, but subsequent exposure leads to a more visible reaction.

	Occurrence of nickel allergy

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
Within orthodontics, nickel is one of the most commonly used metals, as it is a component of the super elastic and shape memory wires, and is included in stainless steel and other alloys. It has been shown that the level of nickel in saliva and serum increases significantly after the insertion of fixed orthodontic appliances.² Nickel is the most common metal to cause contact dermatitis in orthodontics, with more cases of allergic reactions than all the other metals combined.³ Kerosuo et al. found the prevalence of nickel allergy in Finnish adolescents to be 30 per cent in girls and 3 per cent in boys. This is thought to be due to ear piercing being a major cause of sensitization to nickel, as the prevalence in subjects with pierced ears was 31 per cent and those without pierced ears 2 per cent.⁴ Once hypersensitivity has been established, all oral mucosal surfaces can be involved. Sensitizing patients to nickel through routine orthodontic treatment with fixed appliances has been a concern.⁵ It has been suggested that a threshold concentration of approximately 30 ppm of nickel may be sufficient to elicit a cytotoxic response.⁶ However, it has been stated that oral antigenic contacts in non-sensitized individuals may induce tolerance to nickel, rather than sensitization.⁷ Nickel sensitization is believed to be increased by mechanical irritation, skin maceration, or oral mucosal injury, all of which may occur in orthodontic treatment. Environmental temperatures and duration of exposure may also be factors. The lesions of contact stomatitis may be variable and may be barely visible. Itching is not a common feature of contact stomatitis (see Table 1)⁸ and extra-oral reactions are more common than intra-oral reactions.

	Diagnosis of nickel allergy

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

• previous allergic response after wearing earrings or a metal watchstrap;
  
• appearance of allergy symptoms shortly after the initial insertion of orthodontic components containing nickel;
  
• confined extra-oral rash adjacent to headgear studs.
  

A dermatologist should confirm the diagnosis by patch testing using 5 per cent nickel sulphate in petroleum jelly.

Lesions due to other causes should be eliminated:

• candidiasis;
  
• herpetic stomatitis;
  
• ulcers due to mechanical irritation;
  
• allergies to other materials such as acrylic.
  

All adverse reactions to any orthodontic material should be reported on an ‘Adverse Reaction to Dental Materials’ reporting form obtainable from Adverse Reaction Reporting Project, Centre for Biomaterials and Tissue Engineering, Department of Restorative Dentistry, University of Sheffield, Sheffield S10 2TA, UK.

	Alternative materials for nickel allergy patients

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
The potential for orthodontic metals to cause allergic reactions is related to the pattern and mode of corrosion, with subsequent release of metal ions, such as nickel, into the oral cavity. This is dependent not only on the composition of the metal, but also the temperature, pH of the environment, and wear of the wire due to friction from sliding mechanics, abrasion, presence of solder, and strain of the wire.⁹ Stainless steel contains 8 per cent nickel, whilst nickel-titanium wires may contain in excess of 50 per cent.

Archwires
Stainless steel. The majority of investigations have found that nickel sensitive patients are able to tolerate stainless steel without any noticeable reaction and this is thought to be due to the crystal lattice of the alloys binding the nickel, which is then not free to react.¹⁰ The only publications to report an allergic response to stainless steel wire are those where the stainless steel was used for intermaxillary or internal fixation, had increased nickel content and were not tested for corrosion.^11,12 Most research concludes that stainless steel is a safe material to use for all intra-oral orthodontic components for nickel sensitive patients. Reduced nickel content stainless steel is also available, but appears to be unnecessary.

Nickel-titanium. Flexible nickel-titanium wires release increased amounts of nickel and are thought to induce nickel sensitivity: there may be up to 20 per cent conversion rate.⁹ These high nickel content wires should be avoided in nickel sensitive patients. Alternatives include twistflex stainless steel, fibre-reinforced composite archwires. Wires such as TMA, pure titanium, and gold-plated wires may also be used without risk. Altered nickel-titanium archwires also exist and include plastic/ resin-coated nickel-titanium archwires.¹³ Ion-implanted nickel-titanium archwires have their surface bombarded with nitrogen ions, which forms an amorphous surface layer, conferring corrosion resistance and displacing nickel atoms. Manufacturers claim that these altered nickel-titanium archwires exhibit less corrosion than stainless steel or non-coated nickel-titanium wires, which results in a reduction of the release of nickel and decreases the risk of an allergic response (see Table 2).

• ceramic brackets produced using polycrystalline alumina, single-crystal sapphire, and zirconia;
  
• polycarbonate brackets that are produced from plastic polymers;
  
• titanium brackets;
  
• gold-plated brackets.
  

Manufacturers are becoming more aware of the concern of nickel allergy and many are producing ‘nickel-lite’ stainless steel versions (see Table 2). The cost implications of treating a nickel sensitive patient with fixed appliances range from an increase of 30 per cent for ‘nickel-lite’ brackets and archwires, to in excess of three times the average cost of particular aesthetic brackets and archwires. Extra-oral metal components, including metal studs in headgear, are of greatest concern due to greater sensitivity of the skin. Plastic-coated headgear studs are available and may be a better alternative to simply wrapping a bandage around the metal component (see Table 3).

	Conclusion

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

	References

Top Abstract Introduction Biology of the reaction Occurrence of nickel allergy Diagnosis of nickel allergy Alternative materials for nickel... Conclusion References

 
1 van Loon, LA, van Elsas PW, Bos J D, ten Harkel-Hagenaar HC, Krieg SR, Davidson, CL. T-lymphocyte and Langerhans cell distribution in normal and allergically-induced oral mucosa in contact with nickel-containing dental alloys. J Oral Path 1988; 17: 129–37.

2 Aaolu G, Arun T, Izgü B, Yarat A. Nickel and chromium levels in the saliva and serum of patients with fixed orthodontic appliances. Angle Orthod 2001; 71: 375–79.[Medline]

3 Lowey MN. Allergic contact dermatitis associated with the use of Interlandi headgear in a patient with a history of atopy. Br Dent J 1993; 17: 67–72.

4 Kerosuo H, Kullaa A, Kerosuo E, Kanerva L, Hensten-Pettersen A. Nickel allergy in adolescents in relation to orthodontic treatment and piercing of ears. Am J Orthod Dentofac Orthop 1996; 109: 148–54.[Medline]

5 Bass JK, Fine H, Cisneros GJ. Nickel hypersensitivity in the orthodontic patient. Am J Orthod Dentofac Orthop 1993; 103: 280–5.[Medline]

6 Bour H, Nicolas JF, Garrigue JL, Demidem A, Schmitt D. Establishment of nickel-specific T cell lines from patients with allergic contact dermatitis: Comparison of three different protocols. Clin Immunol Immunopathol 1994: 73: 142–5.[CrossRef][Medline]

7 Vreeburg K J, de Groot K, von Bloomberg M, Scheper R. Induction of immunological tolerance by oral administration of nickel and chromium. J Dent Res 1984; 63: 124–8.[Abstract/Free Full Text]

8 Park HY, Shearer TR. In vitro release of nickel and chromium from simulated orthodontic appliances. Am J Orthod 1983; 84: 156–9.[CrossRef][Medline]

9 Jia W, Beatty MW, Reinhardt RA, Petro TM, Cohen DM, Maze CR, Strom EA, Hoffman M. Nickel release from orthodontic archwires and cellular immune response to various nickel concentrations. J Biomed Mat Res 1999; 48: 488–95.[CrossRef][Medline]

10 Toms AP. The corrosion of orthodontic wire. Eur J Orthod 1988; 10: 87–97.[Abstract/Free Full Text]

11 Shriver WR, Shereff RH, Domnitz JM, Swintak EF, Civjan S. Allergic response to stainless steel wire. J Oral Surg 1976; 42: 578–81.[CrossRef]

12 Guyuron B, Lasa CI. Reaction to stainless steel wire following orthognathic surgery. Plast Reconstruct Surg 1992; 89: 540–2.[Medline]

13 Kim H, Johnson J. Corrosion of stainless steel, nickel-titanium, coated nickel-titanium, and titanium orthodontic wire. Angle Orthod 1999; 69: 39–44.[Medline]

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