INTRODUCTION:

Austenitic stainless steel used in orthodontic braces contains 18% chrome, 0.15% carbon and 8% nickel. The literature demonstrates that nickel is potentially allergenic and capable of causing a late-phase, type IV hypersensitivity reaction^[1].Nickel is one of the most commonly used metals, as it is a component of nickel-titanium and stainless steel alloys which are widely used in orthodontic appliances. Nickel-titanium alloys may have nickel content in excess of 50 percent and can thus potentially release enough nickel in the oral environment to elicit manifestations of an allergic reaction^[2].

Nickel is a known allergen. In a study of Finnish adolescents, the prevalence of nickel allergy was found to be 30% in girls and 3% in boys. This was thought to be related to sensitization to nickel by ear piercing as the prevalence in adolescents with ear piercing was 31% and only 2% otherwise^[3].

A large variety of metallic alloys are routinely used in dentistry. Allergy as a possible factor has also been implicated in root resorption and hypodontia^[4].

Studies have shown that nickel ion liberation from orthodontic appliances is capable of provoking allergic reactions in the oral cavity. A directly proportional relationship between the concentration of nickel ions liberated and the concentration of nickel in the alloy was found. This situation has provoked the metallurgical industry to support research seeking hypoallergenic orthodontic accessories. Accessories made with low concentrations of nickel, known as nickelfree brackets, have appeared as a material capable of liberating lower quantities of nickel ions, which suggests a lower sensitivity and is therefore ideal for patients hypersensitive to this metal^[5].

METHODS:

Search Stratergy:

A search was conducted in PubMed to retrieve all available literature on allergy and orthodontics and the use of nickel free brackets. The search terms used were ‘allergy’, ‘orthodontics’ and ‘nickel free braces’.

Properties of Nickel:

Nickel is a chemical element, with atomic number 28^[3]. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four elements that are ferromagnetic around room temperature. The metal is corrosion- resistant, finding many uses in alloys as a plating agent, in the manufacture of coins, magnets, common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Nickel is essential for certain plants and animals. Nickel compounds are ubiquitous and are consumed as a part of normal diet from foods such as vegetables, with the daily intake^[3]. Nickel is a component of certain enzyme systems in humans and is considered an essential trace element.

Biology of The Reaction:

An allergic response is one in which certain components of the immune system react excessively to a foreign substance^[4]. Nickel elicits contact dermatitis, which is a type IV delayed hyper sensitivity immune response. This process has two distinct phases; Sensitization phase -first exposure and Elicitation phase - re-exposure to allergen. Elicitation of an allergic reaction to nickel depends on the conditions of nickel exposure—for example, hapten concentration on the contact area, open or occluded exposure, presence of an irritant, and degree of contact allergy. There may have been no symptoms at the initial exposure, but subsequent exposure leads to a more visible reaction^[4-6].

Clinical Features Associated With Allergy:

Clinical abnormalities, such as gingivitis, gingival hyperplasia, lip desquamation, multiform erythema, burning sensation in the mouth, metallic taste, angular cheilitis, and periodontitis, may be associated with release of nickel from orthodontic appliances. A burning sensation is the most frequent symptom. The aspect of the affected mucosa is also variable, from slight erythema to shiny lesions, with or without edema. Vesicles are rarely observed, but when they are present, they quickly rupture, forming erosion areas. Other symptoms can also be present, such as perioral dermatitis and, rarely, orolingual paresthesia^[7-8].

Extensiveness of Allergy:

The incidence of Ni induced side effects from orthodontic materials in non sensitized people is not known. It has also been suggested that the risk of sensitization from orthodontically derived Ni in these patients is extremely low^[9]. Nickel allergy is the most common contact allergy in industrialized countries. Several studies have shown that a higher percentage of females are affected than males. Adolescent females showed more prevalence to allergy than the male population owing to the cause of ear piercing being a major cause of sensitization to nickel, as prevalence in subjects with pierced ears.

People with cutaneous piercing were considered a significant risk factor for Ni allergy. Scientific evidence suggests that orthodontic treatment is not associated with increase of Ni hypersensitivity, unless patients have a history of previous cutaneous piercing exposure to Ni, usually ear piercing^[10].

Periodontal Status In Nickel Allergy:

Placement of orthodontic brackets influences the accumulation of biofilm and colonization of bacteria, thereby making a patient more prone to inflammation and bleeding. Such reactions are characterized by gingival hyperplasia, changes in color and gingival bleeding upon probing. More than a direct sensitizing agent of skin and mucosa, nickel appears to alter the periodontal status, acting as a modifying factor of periodontal disease in sensitive patients^[11].

It was found that low dose continuing nickel release from orthodontic appliances might be the initiating factor for gingival overgrowth, as it has the capability of increasing epithelial cell proliferation. Another finding suggested that patients treated with conventional braces exhibited greater periodontal alterations than those treated with nickel free braces. Individuals with an allergy to nickel exhibit better periodontal health when treated with nickel free braces than with conventional braces. Nickel can influence the condition of the periodontal and blood cells of allergic orthodontic patients, but with reactions of an inflammatory, rather than allergic nature^[12].

Diagnosis of The Allergy:

Sensitivity to nickel has been evaluated through biocompatibility tests, including cutaneous sensitivity (patch) tests, and reactivity to nickel has been evaluated with in vitro cell proliferation assays. It is important to make correct diagnosis of nickel allergy, symptoms of which may occur either within or remote to the oral environment^[13]. The following patient history would suggest a diagnosis of nickel allergy^[14]

• Previous allergic response after wearing earrings or a metal watchstrap;

· Appearance of allergy symptoms shortly after initial insertion of orthodontic components containing nickel;

• Confined extra oral rash adjacent to headgear studs.

Root Resorption And Its Role In Allergy:

Root resorption is a common sequel to orthodontic treatment and has been recorded in 93% of treated adolescents. The incidence of asthma, allergies and signs indicative of psychological stress were significantly higher in patients who had experienced excessive root resorption during orthodontic treatment as compared with the group of orthodontic patients who had completed their course of treatment without suffering this unfortunate outcome. It found that allergy and asthma might be an etiological factor in excessive root resorption^[17].

Hypodontia And Allergy:

Third molars are the most commonly missing teeth followed by the second premolars and the maxillary lateral incisors. The etiology of hypo dontia is considered to be multifactorial, with genetics and environmental factors playing an important role ^[18]. They concluded that health problems, especially those related to allergy, are of importance and could be strongly related to hypodontia.

Management of Nickel Allergy::

The majority of investigations have found that nickel sensitive patients are able to tolerate stainless steel without any noticeable reaction. Most research concludes that stainless steel is a safe material to use for all intra oral orthodontic components for nickel sensitive patients ^[15].

Alternatives To Nickel Titanium Wires:

Alternatives to Ni Ti include twistflex stainless steel and fiber reinforced composite archwires. Wires such as TMA, pure titanium, and gold plated wires may also be used without risk. Nickel titanium archwires have their surface bombarded with nitrogen ions, which forms an amorphous surface layer and reduces the risk of allergy ^[16].

Stainless steel brackets are generally considered safe. However, nickel free alternative brackets to stainless steel include:

· Ceramic brackets produced using polycrystalline alumina, single crystal sapphire, and zirconia;

· Polycarbonate brackets that are produced from plastic polymers;

· Titanium brackets;

· Gold plated brackets.

CONCLUSION:

Safe and effective practice depends on identifying patients with allergy along with knowledge of materials that can potentially cause them. It is imperative for a practitioner to not only know the physical and mechanical properties of the materials being used, but also of the biologic compatibility of the material. Knowledge of alternatives to allergy causing materials is also of prime importance in efficient management of patients in routine clinical practice.

REFERENCES:

1. Camila Alessandra Pazzini, Leandro Silva Marques, Luciano José Pereira, Patrícia Corrêa-Faria, Saul Martins Paiva. Allergic reactions and nickel-free braces: A systematic review. Braz Oral Res. 2011 Jan-Feb;25(1):85-90

2. Preeti Agarwal, Utkarsh Upadhyay, Ragni Tandon, Sanjay Kumar. Nickel allergy and orthodontics. Asian Journal of Oral Health & Allied Sciences - Volume 1, Issue 1, Jan-Mar 2011.

3. Narendra Padiyar, Piyush Tandon, Shobhit Agarwal. Nickel allergy -Is it a cause of concern in everyday dental practice. Int journal of contemporary dentistry. January 2011 2(1).

4. Sunitha Chakravarthi, Sridevi Padmanabhan, Arun B. Chitharanjan. Allergy and orthodontics. Journal of Orthodontic Science, Vol. 1(4) Oct-Dec 2012.

5. Mariele Cristina Garcia Pantuzo, Elton Gonçalves Zenóbio, Helenice de Andrade Marigo, Madelon Aparecida Fernandes Zenóbio . Hypersensitivity to conventional and to nickel-free orthodontic brackets. Braz Oral Res 298 2007;21(4):298-302 .

6. Suchita Madhukar Tarvade, Sheetal Ramkrishna Nickel allergies in orthodontics. Journal of Orthodontic Research , vol 3 (3) Sep-Dec 2015 Janson GR, Dainesi EA, Consolaro A, Woodside DG, Freitas MR.Nickel hypersensitivity reaction before, during, and after orthodontic

7. therapy. Am J Orthod Dentofacial Orthop 1998;113: 655‑60

8. Starkjaer L, Menné T. Nickel allergy and orthodontic treatment. Eur J Orthod 1990;12:284-9.

9. Schafer T, Bohler E, Ruhdorfer S, Weigl L, Wessner D, Filipiak B, et al. Epidemiology of contact allergy in adults. Allergy 2001;56:1192-6.

10. 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.

11. Pazzini CA, Junior GO, Marques LS, Pereira CV, Pereira LJ. Prevalence of nickel allergy and longitudinal evaluation of periodontal abnormalities in orthodontic allergic patients. Angle Orthod 2009; 79:922-7.

12. Pazzini CA, Pereira LJ, Carlos RG, de Melo GE, Zampini MA, Marques LS. Nickel: Periodontal status and blood parameters in allergic orthodontic patients. Am J Orthod Dentofacial Orthop 2011;139:55-9.

13. Wataha JC. Biocompatibilty of dental casting alloys: A review. J Prosthet Dent 2000;83:223‑34

14. Rahilly G, Price N. Nickel allergy and orthodontics. J Orthod 2003;30:171-4

15. Toms AP. The corrosion of orthodontic wire. Eur J Or thod 1988;10:87-97

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

17. Kurol J, Owman Moll P, Lundgren D. Time related root resorptions after application of a controlled continuous orthodontic force. Am J Orthod Dentofac Orthop 1996;110:303-10

18. Symons AL, Stritzel F, Stamation J. Anomalies associated with hypodontia of the permanent lateral incisors and second premolars. J Clin Pediatr Dent 1993;17:109-11.

Received on 30.05.2016 Modified on 17.06.2016

Research J. Pharm. and Tech 2016; 9(9):1516-1518.

DOI: 10.5958/0974-360X.2016.00296.1