Oral Medicine

Allergies to dental materials

William A. Wiltshire*/Mat7na R. FeiTeira**/At J. Ligthelm***

Abstract Allergies related to generally constitute delayed hypersensitive reactions to specific dental tnaterials- Although true allergic hypersensitivity to dental materials is rare, certain products have definite allergenic properties. Extensive reports in the literature substantiate that certain materials catise allergies in patients, who exhibit ntueosal and skin symptoms. Currently, however, neither substantial data nor clinical experienee unequivocally contraindícate the discontinuance of any ofthe tnaterials. which inchtde dental ainalgain and nickel- and chromium-containing metals. The dentist fortns a vital link in the teatn approach to the differential diagnosis of allergenic biomaterials that elicit symptoms in a patient, not only Intraorally. but also on unrelated parts ofthe body (Quintessence Int ¡996:27:513-520.)

Clinical relevance circulating antibodies, because the causative agents attain their allergenic properties by combining with the Although the dentist should be aware of the mucosal tissues ofthe patient. The delayed hypersen- sitive reaction is not manifested clinically until several allergenic materials used in practice, which include hours after exposure.' acrylic resin, amalgam, impression materials, euge- nol products, and metal products, particularly A contact allergy in dentistiy is the type of reaction nickel, currently neither substantial data nor clinical in which a lesion of the skin or mucosa occurs at a localized site after repeated contact with the allergenic experience unequivocally contraindicates the dis- material.' The ability to cause contact sensitivity continuance of any ofthe materials. appears to be related to the ability of the simple chemical allergen to bind to proteins, especially those ofthe epidermis,- and. in dentistry, specifically the oral

Introduction Allergic hypersensitivity related to dentistry is acquired Contact dermatitis by exposure to specific allergens atid Clinical features the altered capacity of the patient to react when re-exposed to the allergen, Allei^ic reactions associ- As in all forms of eel I-mediated immunity, in contact ated with dental materials are generally delayed hyper- dermatitis there is a minimum latent period of at least 5 sensitive reactions that are usually not associated with days between the first contact with the allergen and the ability to react at a distant site to further contact with a nonirritant concentration of the allergen. Reactions * Professor and Head, Departtnent of Orthodontics, University of take between 24 and 48 hours to develop and, if severe, Pretoria, Faeiilty of Dentistry, Pretoria, South Africa may last for 7 to 10 days.- *' Ftead Emeritus; Division of Dental Materiais, University ofPreturia, Contact dermatitis is manifested by an itching or Faculty of Dentiïtrj', Pretoria, South Afriea, burning sensation at the site of contact, followed a *** Professor and Head, Department of Orai Pathology, University of short while later by the appearance of erythema and Pretoria, Faculty of Dentistry, Pretoria, South Afriea, then vesicles. Once the vesicles have ruptured, the Reprint requests: Prof W A. Wiitshire. Department of Orthodontics, erosion may become more extensive, and secondary University of Pretoria, c/o PO Box 73752, Lynnwood Ridge, Pretoria 0040, South Africa, infection may develop,'

Quintessence International Volume 27, Number 8/1996 513 Wiltshire et al

This article will review allergic hypersensitivity to various modern dental materials.

Allergenic dental materials Acrylic resin Acrylic resin has been reported to occasionally induce an allergic hypersensitivity when used as a denture base, restorative material, or provisional fixed partial denture resin (Fig 1 ), Normally, the patient is exposed to the free monomer in acrylic resin, which may causea toxic reaction, Hypersensitivily in denture wearers should not be confused, however, with physicai Fig 1 A suspected allergic reaction lo a self-cunng acrylic irritation of the oral mucosa caused by ill-fitting resin provisional fixed partiai denture piaced in thG maxillary dentures. Acrylic resin hypersensitivity may develop anterior segment has developed at the corners of tine mouth a few days toiiowing placement. The reaction is characte- shortly after insertion of the denture or may not rized by itching, vesicular formation, and crusting. The manifest for an extended period of time, even many condition was alleviated when the permanent ceramometal months' (Figs 2a and 2b), Clinical reactions may fixed partial denture was placed 9 days later occur at secondary sites (Figs 3a and 3b),

Resit) composite Lind^ reported that resin composite materials could be The oral man ¡testa lions, known as contact stomatitis an etiologic factor in the development of lichenoid or stomatitis venenata, iticlude an inflamed and reactions in the oral mucosa. The pathogenic mech- edematous mucosa, accompatiied by a severe burning anism may be related to contact allergy to formalde- sensation. Small, transiem vesicles may form; these hyde formed in resin composite restorations. Formal- rupture to fonn areas ol" erosion and ulcération.' dehyde causes more than one third of all allergic Erythema, papules, and edema are characteristic reactions caused by dental materials, A report by ailergic manifestations and, in severe reactions, large 0ysaed et al^ indicated that formation of formaldehyde weeping blisters may appear," Stomatitis venenata was found in light , ultraviolet light-, and chemically occurs iess frequently than do allergic skin lesions. activated resin composites, This can be ascribed to the diluting, digestive, and washing effects of saliva, Itnpression materials Ahhough certain dental materials have been im- Polyether impression materials have been reported to plicated as causes of contact stomatitis, the reported cause allergic problems in the past, but have since incidence is low. However, wheti an ofFending dental changed their compositions. Care should be taken to material sensitizes an area ofthe mucosa, no matter mix the material thoroughly and to avoid contact ofthe how small the area, the individual may become aromatic sulfuric ester catalyst paste with the skin or sensitized,^ mucosa because it may elicit adverse tissue reactions,

Treattnent and prognosis Ettgenol-containing products Several tnethods of treating allergies have been re- Oil of cloves, or in its unrefined form, is mixed ported, including íiymplomatic treatment, desensiti- with to form zinc oxide-eugenol (ZOE), zation, and elimination of the allergen. Because the which exhibits a combination of physical and thera- mechanism of the allergic reaction is not yet ftilly peutic properties making it useflil as a provisional understood, the presently recommended method of restorative materiai, base material, and may be elimination of the ailei^en."' Pres- filling material. Zinc oxide-eugenol impression pastes ently, the only effective treatment for contact dermatitis and ZOE periodontal packs are also available. Euge- or stomatitis is the discontinuance of all contact with nol is highly soluble and is continuously released from the allei^enic material, which usually results in prompt ZOE, which can lead to short-term saturation ofthe remission of all the lesions. oral environrnent with eugenol in a concentration

514 Quintessence International Volume 27, Number 8/1996 Wiltshire et al

Fig 2a The upper lip and eyelids are severely swollen 5 days a¡ter insertion of provisional acrylic resin fixed parfial denture.

Fig 2b One week after removal of Ihe provisional acrylic resin prosthe- sis and after replacement with a permanent ceramometal fixed par- tial denture, the swelling is gone.

Fig 3a (/eW An allergic reaction may occur at a secondary site in acrylic resin allergy After placement of a new maxiiiary complete denture, a secondary allergic reaction occurred on the inside ol this patient's upper legs.

Fig 3b (below) The inside of the patienfs arm, and his stomach and back, were also affected.

sufficient to cause cytotoxicity. This is why eugenol context the cross reactivity between many allergenic periodontal packs, which are in contact with open substances, such as between eugenol and balsam of mucosal wounds, are no longer popular. Peru, should be borne in mind. Thus, when the causative Five ofthe periodontal dressing materials listed in agent in an allergic reaction to periodontai dressing Accepted Dental Therapeutic^ contain colophony materials has not been positively identified, a choice (resin), and four of them contain eugenol. The only among the materials, whether they are eugenol-frcc or one that is eugenol free (Coe-pak, Coe Laboratories) not, is impossible.^ contains, among other things, balsam of Peru.^ In this

Quintessence International Volume 27, Number 8/1996 515 Wiltshire et al

Fig 4 Suspected allergy to an amalgam alloy has caused Fig 5 Suspected allergic contact glossitis has developed erythema and vesicle formation. The symptoms disappear- adjacent to a gold crown The swelling and erythematous ed after a resin composite restorative material was placed. changes disappeared after the restoration was replaced with a porcelain orown.

The inilatumatory response caused in mucosal Vernon et al "' reviewed 41 published cases of allergy tissue by eugenol should not, however, be confused to dental amalgam, which included 30 female and U with allergic hypersensitivity. From a biologic point of male patients. Twenty of the 41 patients recovered oa view. ZOE is in fact considered the least damaging removal of their amaigam restorations. The most restorative material and possesses sedative or anodyne frequent symptoms were of the remote cutaneous type propetiies, which are very useful in dentistry."^" (38 of 41 cases), while local symptoms, particularly Despite the advantageous properties of eugenol, how- gingivitis and stomatitis, occurred in 17 cases. The ever, sensitivity, tnanifested as positive inflammatory authors suggested that the figures probabiy under- responses to eugenol in certain root canal sealers has estimate the true prevalence of the condition because been described,'- of underreporting of cases. Mercury was found to be the most common sensitizing agent, but other metals, particularly copper, zinc, and silver, could also be Metals implicated." Amalgam Gold Althoughrare.allergyto mercury'-'as well as copper in amalgam'"* has been described. In addition, the release Gold is generally regarded as an inert and safe of mercury from amalgam restorations has been the material,-' but the belief that gold is nonsensitizing is cause of skin and mucosal disorders'^ (Fig 4). There is not substantiated by reported data. Comaish'^ re- also growing evidence that amalgam restorations may ported allergic dermatitis to a gold wedding ring, be etiologic factors in some of the mucosal changes Elgart and Higdan'** described stomatitis caused by a classified as oral lichen pianus.'^ Some of these gold and concomitant dermatitis at disorders may be considered a mucosal pattern of sites in contact with gold jewelry worn by the patient. response to several distinct pathogenic factors. Ailergy The number of confirmed cases of gold sensitivity is to amalgam compounds may be one such pathogenic extremely low^ (Fig 5), mechanism." ln many cases, electrogalvanism may enhance the allergic reaction as a transmitter of Nickel reactive ions, justifying the term electrogalvanic white In general, nickel, ranJted third among the five most lesion, used by Bánóczy et al.'^ common causes of allergic contact dermatitis-" and Because erosive forms of oral lichen planus are first in most industrialized countries, is the most known to be susceptible to cancer deyelopment, common contact allergen in dentistry affecting females patients should be given effective causal treatment.'^ in Europe and the United States.'' Nickel hypersen-

516 Quintessence International Volume 27, Number Wiltshire et al

Fig 6a (left) Nickel dermatitis of the earlobe is common in niokef-sensilive individuals who v^iear nickel-containing jewelry.

Fig 6b (below) Swelling and erythema of the earlobe are evident after removal of the earring.

sitivity is found more frequently among women than among men.-* Aboul 10% of females are sensitive to nickel, and the majority become sensitized through jewelry,-- although one repot! indicates that up to 20% of females are sensitive to nickel.-- Nickel dermatitis of the earlobe is common in nickel-sensitive females-' (Figs 6a and 6b). Only 1% to 2% of males are found to be nickel sensitive, indicating a striking sex differ- ence.-^-'' The signs and symptoms of nickel sensitivity often are manifested when nickel-containing gold jewelry, suchas watches (Fig 7) and bracelets, is worn. With the increased popularity of metal-framed eye- wear, a new source of prolonged contact with nickel has arisen. Fig 7 Contact dermatitis has developed after ej^Dosure to Nickel accounts for between 64% and 78% ofthe nickel in a watchband. composition of some nickel-based base metal alloys. Nickel has been found to produce more contact dermatitis than all other metals combined, and even However, such spreads to secondary sites may be partial denture frameworks containing as little as 1.5% caused by contaminated, perspiring fingers of the nickel have been reported to cause contact dermatitis,-^ patient during the initial eruptive stage. ^ indicating that the allergic response is virtually dose In orthodontics, allergic reactions to nickel in independent in a sensitized individual. Reactions to cervical headgear-' as well as allergic reactions to nickel at extraoral sites at areas of contact with orthodontic wires-^ and nickel-titanium orthodontic chromium-plated jewelry, as well as at areas totally wires, have been reported. However, a recent study did unrelated to direct exposure to metal have also been not find that nickel-sensitive persons are at greater risk reported.-^ of developing discomfort in the oral cavity when Clinical reactions to nickel include edema of the wearing an intraoral orthodontic appliance.-' eyelids, swollen and fissured lips, and chronic eczema Despite the reported allergenicity of nickel, few of the cheeks and palms.^'^ Nickel dermatitis can cases of adverse reactions to nickel-containing dental spread symmetrically to secondary sites snch as the prostheses have been reported. The evidence that arm, eyelids, sides ofthe neck, and face.^ How nickel nickel absorption intraorally exacerbates existing der- dennatitis spreads to distant areas is not known. matitis is also minimal. Furthermore, there is little

Quintessence International Volume 27, Number 8/1996 517 Wiltshire et al evidence available to implicate nickel as playing any Restorations part in the rejection of nickel-containing prostheses, Recently, Suzuki^^ ^¡^^¿ ^^^ ^-ray fluorescence spec- dental or orthopedic,-^ and it must be concluded that troscope to detect the allergenic metals in intraoral nickel materials are generally safe to use in dentistry. metal restorations and personal and household itetns of metal-allergic patients, Ofthe 275 subjects who had Chromate positive reactions to M-9 series patch tests, the 10 Chromium differs from nickel in that it is not antigenic most common elements detected for restorations were in metal form, but usually only in the hexavaletit salt silver, copper, zinc, gold, palladium, tin, mercury, form as chromate. Minute quantities of chromium salts indium, nickel, and chronnium. Allergens were de- can, however, sensitize. Chromium compounds, on tected in 161 patients, and the five elements wilh the other hand, can induce cotitact dermatitis and even higher allergetiicity were mercury, nickel, tin, chro- cause severe corrosive irritation ofthe skin. Exposure mium, and cobalt. In personal and household items, normally occurs due to industrial exposure or through the top five elements with higher allergenicity were handling or use of detetBents, bleaches, shaving copper, nickel, chromium, zinc, and molybdenutn, creams, lotions, matches, and chromated catgut,-* Suzuki'- concluded that metal allet^y should be However, it has been found that neither chromium- taken into consideration whenever dental treatments containing alloys nor chromium-plated objects, such with alloys are planned. For patients with metal as jewelry, produce allergic contact dertnatitis in allergies, as well as for those without, it is prudent to chromium-sensitive individuals. Although allei^ic avoid the use of mercury, nickel, and other elemetits reactions resulting from contact with chromium-type with a high sensitization rate, if possible, Eveti alloys do occur, such allergies are usually due to some precious metals, such as gold or platinum, may cause other metal in the alloy, normally nickel.-' allergies, especially for individuals with a history of Although base tnetal alloys contain between 11 % direct contact with intradermal tissues. It is recom- and 35% chromium,-* chromium allergy is rarely seen. mended that similar types of alloys be used in a single It is a less common problem than is nickel allergy. The oral environment, where possible, to prevent corro- chances of an adverse reaction to chromium found in sion and dissolution by intraoral electric current.'^ dental materials, therefore, appears to be remote,--'-^ Hildebrand et al^^ reported on 139 published cases but clinicians should nevertheless always be on the of allergy to dental restorations. The most frequent alert. symptoms were local gingivitis and stomatitis (99 of 139} while general and remote symptoms occurred in Platinum 33 patients. Ninety-two female and 47 male patients were involved. In another review, the same authors^'' Documented cases of platinum hypersensitivity are reported that allergic reactions to nickel, cobalt, and even more rare than is chromium allergy, Platinosis is chrotnium in dental prostheses and restorations tnay not caused by metallic platinum but by contact with appear either locally as stomatitis or distantly in the complex platinum salts and mainly affects platinum form of general or local contact dermatitis. refiners. Manifestations include pruritis, erythema, eczema, and urticaria, usually limited to the exposed parts ^^" Allergy testing Allergy testing of dental materials consists of epicuta- Cobalt neous patch testing, in which readings of skin reac- Cobalt-chromium alloys, forming the framework of tions are made on removal of patches after 48. 72, or metal partial dentures, and base metal alloys contain 96 hours. The presence of erythema, combined with about 60% to 65% cobalt. They are regarded as edematous infiltration with or without papules or biocompatible because of the absence of nickel and vesicles, is used as the criterion for a positive result,^^ beryllium in their composition. Cobalt is nevertheless There is no need to perfonn an epimucous test to listed as a sensitizing metal. Allergic reactions to detect contact allergy in the oral mucosa, because the cobalt used in dentistry are very rare, however. In epicutaneous test gives the applicable information.'^ patients with no known allergy, preventive screening is Axell et al" designed a hst for patch test screening unnecessary, ^^•^' of dental materials in cooperation with The Nordic

518 Quintessence International Volutne 27, Number 8/1996 Institute of Dental Materials (NIOM), This patch test indicates the discontinuance of any ofthe materials, series (dental screening) consists of 21 chemicals. The including mercury-, nickel-, chromium-, or eugenol- substances used in the list were chosen from reports in containing dental materials,^'^^ Nevertheless, it is the literature on contact allergic reactions to dental advisable to ask patients questions concerning past materials. The dental screening test series was devised hypersensitivity to dental materials or following dental for use mainly in the investigation of patients with procedures. As pari of the medical history, each stomatitis, to ritle out a possible allergic reaction patient should also be specifically asked whether a rash to a component in the dental materials used. In the or eczema had ever developed following the wearing of dental screening test series, the main group of com- earrings or jewelry. pounds is the methacrylate monomers, which are In most patients, there is no indication for patch fundamental in dental resin materials, such as resin testing. Routine use of such a test for all patients cotnposite restorations, pit and fissure sealants, resin should be avoided, because the test procedure tnay in bonding materials, resin veneering materials, and some cases provoke sensitization ofthe patient.-'^ The denture base materials. Triethylene/glycol dimethacry- main indication for an ep i cutaneous test is the latc (TEGDMA); urethane dimethacrylate (UDMA); presence of local symptoms in the mouth close to a ethyleneglycol dimethacrylate (EGDMA); bisphenol dental restoration or prosthetic or orthodontic ap- A-glycidyl methacrylate (bis-GMA) as well as accel- pliance. erators (N,N-dimethyl-p-to]uidine and 2-hydroxy-4- When skin symptoms are present, the patient should metttoxybenzophenone); aromatic sulfuric esters (meth- be referred to a dermatologist for consultation. The yldichloroberrzene sulfonate); eugenol; colophony; epicutaneous test should be undertaken by a dermatol- nickel sulfate; copper sulfate; and formaldehyde, ogist.^^ Once a positive test has been confirmed by the among others, are included in the test series.^^ dermatologist, the offending material should be with- More recently, Axell et al-'^ described a new method drav/n. Rapid remission ofthe symptoms will confirm for intraoral patch testing in which maxillary acrylic the positive allergy test, and the patient should be resin plates carrying test pieces contaitting 66% nickel made aware of his or her aüergie status and be advised were applied for 48 hours. Readings were performed to report it to future dental practitioners, A repeat test 24 hours after removal. Although few, if any, clinical may be necessary for true confirmation of allergy, but signs were elicited in three test suhjects, two of whom because of ethical considerations, may not be clinicaUy were contact sensitive to nickel, biopsy specimens possible. from the mucosal contact sites revealed lichenoid The dentist forms an important link In the differen- reactiorrs. Biopsy specimens from control sites showed tial diagnosis of allergy. Ail possible allergenic dental no or slight nonspecific inflammatory reactions.^^ The materials should be considered when allergic patients use of biopsy testing for allergy may raise ethical with symptoms, whether intraoral or on unrelated problems, however. parts ofthe body, are tested. Although not allergy testing per se, the Fleigl test, a simple, inexpensive, and reliable test, has also been Acknowledgments used^ to determine which metal objects produce con- The authors are grateful to Mrs Yvonne Skinner, Deparlment of tact dertnatitis irr nickel-sensitive individuals. Place- Orthodontics, for typjni; Lht manuscript, an welt as Kobtis van derMerwe. ment of two or three drops of a 1% alcoholic solution Henriette Rothmann, and Lydia Faber for llie photographic work. of dimethylglyoxime and a few drops of ammonia water on a metallic object, on skin, or in a solution, produces a strawberry-red insoluble salt in the presence of References available nickel. Most rrickel-containing alloys, except stainless steel, yield a positive test. 1. ShaferWO,HineMK,Levj'BM, A textbook of Oral Pathology, ed 4, Philadelphia: Saunders, 1983:582-588, 2. Turk JL, Reactions caused by cell-mediated immune response. In: Volega TM. Inwiunology in Ciinicai Medicine, ed 2, London; William Heineman, 1972:44-59. Recomme nd atio ns 3. HugetF.F, Dental Alloys: Biological considerations. In: Alternatives to Gold Alloys in Dentistry. Conference Proceedings. US Dept of Extensive reports In the literature indicate that certain Health, hducation and Welfare, Public Health Service, NIH, materials in dentistry cause allergic hypersensitivity in 1977'139-164. patients; nevertheless, currently, neither substantial 4. Nakayama H, Nogi N, Kasahara N, Matsuo S, Allergen control, data nor clinical experience unequivocally contra- DermatoiClin 1990;8:197-2O4,

Quintessence Intemalional Volume 27, Number 8/1996 519 Wiltshire et al

5. Lind PO Oral lichenoid reactions retalcd to composite reslorations. 23. Jones TK. Hansen CA. Singer ML. et al. Dentó! implications of Preliminary report. Acta Odontol Scatid 1988^46:63-65. nickel sensitivity. J Prosthet Dent 1986:56:507-509. 6. 0ysaed H, Ruytcr IE. SjBvik Kleven tJ. Formation of fortnaldciiyde 24. AI Wahcidi EMH. Allergie reaction to nickel orthodontic wires: A in dental cotnposites, NOF 70th Annual Meeting. 1987:75. case report. Quintessenee Int 1995;26:3S5-387. 7. O'Brien WJ. RygeG. Impression Materials, Philadelphia: Saunders, 25. Wood JF. Mucosal reaction to cobalt chromium alloy Br Dent] I978;I37-13S. l974;136:423-424. S. Accepted Dental Therapeulics. ed 3S. Chicago: American Dental 26. Kelly JR. Rose TL. Non precious alloys for use in fixed pros- Association. 1975:237-238. thodontics: A literature review. J Prosthet Dent 1983i49:363-37Û. 9. Haugen E, Hensten-Pettersen A. The sensitizing polential of 27. Greig DGM. Contad dermatitis reaclion to a metal buckle on periodontal dresBlngs. J Dent Res 197Si57:95ü-953. cervical headgear. Br J Dent 19K3; 155:61-62. 10. Hanks CT. Anderson M, Craig RG. Cytotoxic effects of dental cements on two cell culture systems. J Oral Pathol 1981:10:101-112. 28. Dunlap CL. Vincent SK., Barker Bl. Allergic reaction to orthodontic wire: Report of case. J Am Denl Assoc 1989; 118:449-450. 11 Hume WR. The pharmacologie and toxico logical properties of zinc oxide-eugenol. J Am Dent Assoc 1986:113:789-791, 29. Wiltshire WA. Nickel and cobalt based alloys for resin-bonded 12 Hensten Pcttersen A, Orstavik D. Wennbeig A. Allergenic potential prostheses. Quintessence Dem Technol Yearbook, 1989; 13:153-160. of root canal sealers. Endod Dent Traumatol 1985;l:fil-65. 30. Roberts AE, Plalinosis. Arch Ind Hyg 196I;4r549-559. 13. Ferastrom AlB, Ftykiiolm KO. Huldt S, Mercury allergy wilh 31 Stenberg T. Release of cobalt and cobalt chromium alloy construc- eczematous dermatitis due to silver amalgam fillings. Br Dent J tions in the oral cavities of man. Scand J Dent Res 1982;9O:472- 1962;I8:204-205 479. 14. FrykholmKO, FrithiofL, Fernslröm AlB. el al. Allergy to copper derived from dental alloys as a possible cause of oral lesions of lichen 32. Suzuki N. Metal allergy in dentistry: Detection of allergen meláis planus. Acta Derm Venereol I969:49:26B-281. with x-ray fluorescence spectroscope and ils application toward allergen elimination. lnl J Prosthodont 1995:8:351-369. 15. Und PO, Hurlen B, Lyberg T, Aas E. Amalgam-related oral lichenoid reaction. Scand J Denl Res 1986:94:448-451. 33. Hildebrand HF. Vemon C. Manin P. Non-precious metal dentai 16 Vemon C, Hildebrand HF Martin R Dental amalgams and allergy alloys and allergy [review!. J Biol Buccale 1989;17r227-243 ireviewJ.J Biol Buccale 1986; 14:83-100. 34. Hildebrand HF. Vemon C. Martin P. Nickel, chromium, cobalt 17. Báncózy J. Roed Petersen B. Pindborg JJ. ltiovay J. CUnical and denial alloys and alleigic reactions: An overyiew. Biotnaterials histologie studies on cleclrogalvanic induced oral white lesions. Oral 1989:10:545-548, Surg 1979:48:319-323. 35. Lundström IMC. Allergy and corrosion of dental materials in 18. Comaish S. A case of contact hypersensitivity lo metallic gold. Arch patients with oral lichen planus. Int J Oral Surg l9S4;13:16-24. Derrnatol 1969:99:720-723. 36. Yontcher E. Hedegard B, Carlsson G. Contact allergy lo dental 19. Elgart ML, Higdon RS. Allergic contact dermatitis to goid. Arch materials in patients with orofacial complaints J Oral Rehabil Dermaiol l97lilO3:649-653. ]986;13:IS3-I9O. 20. Fisher AE. Contact Dermalitis. ed 2. Philadelphia: Lea & Febiger. 37. AxellT. BjörknerB, Fregen S, Mikiasson BO. Standard patch ttst 1973:87-105. series for screening of conlact allergy to dental materials. Contact 21. Staerkjaer L, Menné T. Nickel allergy and orthodontic treatment Dermatitis 1983^9:82-84. EurlOrthod 1990:12:284-289. 38. Axell T. Spiechowicz E, Glantz PO. Andersson G. Larsson A. A 22. Burrows D, Hypetsensitivity to mercury, nickel and chromium in new method for irtra-oraj patch testing. Contact Deimatilis relation to dental malenals. Int Dent J 1986.36:30-34. 1986;15:58-62. 0

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