Allergies in Orthodontics: From Causes to Management

Concern about allergic reactions in orthodontic patients has been expressed regularly. Patients undergoing orthodontic treatment with fixed appliances are exposed to various biomaterials. Awareness of reactions that can occur with these dental materials is important to the orthodontist. The aim of this paper is to review the current literature on allergy in orthodontics and the implications of the allergic reaction in the management of patients during orthodontic treatment. Diagnosis and treatment should include a multidisciplinary team. In all instances, the patient’s well-being should guide treatment decisions, and general health not just oral health should be the goal.


INTRODUCTION
An allergic response is one in which certain components of the immune system react excessively to a foreign substance. Two key allergic reactions have been described in the literature. Type I hypersensitivity reactions are an immediate antibody mediated allergic response, occurring within minutes or hours after direct skin or mucosal contact with the allergen. 1 This reaction ranges from contact urticaria to full-blown anaphylaxis with respiratory distress and or hypotension. A delayed hypersensitivity reaction (Type IV), delayed-type hypersensitivity reactions (Type IV allergic reactions) are allergic immune reactions manifesting primarily through T cells (Cellular immunity). 2 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. It presents with diffuse or patchy eczema on the contact area and may be accompanied initially by itching, redness, and vesicle formation.
There is rising concern about the biocompatibility of dental materials; this might be due to a real increase in the occurrence of allergic reactions to the materials or to an increase in awareness of adverse effects from these materials. 3

Nickel
Nickel alloys are widely used in the orthodontic in brackets, wires, bands and other orthodontic accessories. Nickel allergy occurs more frequently than allergy to all other metals combined. 5 It is estimated that 11% of all women and 20% of women between the ages of 16 and 35 years have a sensitivity to nickel. [6][7][8] Nickel-induced contact dermatitis is a Type IV delayed hypersensitivity immune response occurring at least 24 hours after exposure. 9,10 It has been shown that the level of nickel in saliva and serum increases significantly after the insertion of fixed orthodontic appliances. 11 Nickel leaching from orthodontic bands, brackets, stainless steel or Ni-Ti archwires has been shown in vitro to occur within the first week and then decline thereafter. 12 It is suggested that a threshold concentration of approximately 30 ppm of nickel may be sufficient to elicit a cytotoxic response. 13 14 however, oral exposure to nickel through dental braces prior to ear piercing reduces the risk of developing nickel allergy. 15,16 Previous allergic response after wearing earrings or a metal watchstrap, appearance of allergy symptoms shortly after the initial insertion of orthodontic components containing Nickel and confined extraoral rash adjacent to headgear studs should raise alarm to clinician concerning nickel allergy.
Signs and symptoms of nickel allergy includes gingivitis, gingival hyperplasia, lip desquamation, burning sensation in the mouth, metallic taste, angular cheilitis, and periodontitis. 17,18 In chronic cases, the affected mucosa is typically in contact with the causal agent and appears erythematous or hyperkeratotic to ulcerated. 19 Extraoral manifestations of nickel allergy may have an intraoral origin. 20 If a nickel allergy is still in question, a diagnosis can be confirmed by a dermatologist by conducting a cutaneous sensitivity test called a patch test (Table 1) using 5% nickel sulphate in petroleum jelly. 21 If intra-oral signs and symptoms (Table 2) are present and a diagnosis of nickel hypersensitivity is established, the fixed or removable prosthesis should be replaced with another nickel free alloy. The nickel titanium archwires should be removed and replaced with a stainless steel archwire which is low in nickel content or preferably a titanium molybdenum alloy (TMA) archwire, known as "TMA", which does not contain nickel. 22 Most patients who develop a reaction to Ni-Ti archwires subsequently tolerate stainless steel without a reaction. 23 Other options include Fiber reinforced composite wires, Gold plated wires, Ion-implanted nickel-titanium archwires or Plastic/Resin-coated nickel-titanium archwires. 24 Stainless steel brackets are generally considered safe. 25 However, nickel free alternative brackets to stainless steel include Ceramic brackets produced using polycrystalline alumina, single crystal sapphire, and zirconia, Polycarbonate brackets, Titanium brackets and Gold plated brackets and plastic brackets in selected cases Fixed appliances may be substituted with plastic aligners. Extra-oral metal components, including metal studs in headgear, are of greatest concern due to greater sensitivity of skin. Plastic coated headgear studs may be a better alternative for such patients.

Latex
Natural rubber (Latex) is a milky juice obtained from rubber tree, Hevea Brasiliensis. There has been increase in allergic reactions to natural rubber latex (NRL) over the past two decades due to increased in the use of latex based gloves as universal precaution measures.
Jacobsen and Hensten Pettersen found that, from 1998 to 2000, there had been a ten-fold increase in reported reactions to NRL during orthodontic treatment. 26 Natural rubber latex is found in gloves, intra-and extra-oral elastics, separators, elastomeric modules, elastomeric power chain, polishing rubber cups, band removers.
The allergic compounds from natural latex include chemical substances associated to vulcanization, such as residual proteins and chemical substances from powder or talc.
With latex both type I and type IV hypersensitivity reactions can occur. The prevalence of potential type I hypersensitivity to latex is lower than 1% in the general population and between 6-12% among dental professionals. 27 Immediate (Type I) IgE Antibody mediated response to NRL usually occurs within 5-60 minutes of contact with allergen. Severe   28 More than 10 deaths have been attributed to latex anaphylaxis. 29 It is also known to cause Allergic contact dermatitis.
Contact dermatitis is a T cell mediated, delayed hypersensitivity (Type IV) reaction. The allergens usually responsible for triggering the allergic reaction are the chemical accelerators like thiurams, carbamates and benzothiazoles that are used in the glovemanufacturing process. 28 Allergic contact dermatitis can result in an eczematous rash that is typically pruritic. If the mucosa is involved, it may swell, become erythematous or develop small vesicles. patient may also complain of a burning or itching sensation in the affected area. 30,31 The prevalence of NRL allergy has been reported as being less than 1% in the general population, 5-15% in HCWs and 24-60% in patients with There are a number of latex free alternatives to commonly used orthodontic materials (Table 3). In the latex sensitive patient, steel ligatures or self ligating brackets may be preferred. Elastomeric separators can be replaced with self-locking separating springs. 32 Synthetic non-latex gloves made from nitrile, polychloroprene, elastyren and vinyl, are readily available for clinical use. NRL-free elastics are available but they showed greater hysteresis than NRL elastics i.e. 40% force decay as opposed to 25% over 24 hours. 33 Although NRL-free elastics do not perform as well as NRL elastics in laboratory studies, it is unlikely that the relatively small mechanical differences in force decay would have a clinically significant effect.

Acrylic Resin
Acrylic resins are widely used in dentistry, especially in prosthodontics and orthodontics. It has been reported to occasionally induce an allergic hypersensitivity reaction when used as a denture base or as a restorative material. Acrylic resins based on methylmethacrylate can produce type IV hypersensitivity reactions, which happen after re-exposing a subject to the allergen. 34 Nealey and Del Rio 35

Other Materials
Chromium is the second most frequent metal to cause contact dermatitis. 42 43 The chances of an adverse reaction to chromium found in dental materials, appears to be rare. 44 Similarly documented cases of platinum hypersensitivity are even rarer than chromium allergy. 45 Resin composite materials could be an etiologic factor in the development of lichenoid reactions in the oral mucosa. 46 The pathogenic mechanism may be related to contact allergy to formaldehyde formed in resin composite restorations. Though the chances of an adverse reaction to these dental materials, appears to be remote clinicians should nevertheless always be on the alert.   OJN