READERS’ FORUM

Letters to the editor*

Allergic reactions to acrylicsI write in response to the article, “Allergy to auto-

polymerized acrylic resin in an orthodontic patient”(Gonçalves TS, Morganti MA, Campos LC, Rizzatto SMD,Menezes LM. Am J Orthod Dentofacial Orthop 2006;129:431-5).

Allergic reactions to acrylic materials are certainly real,as we witness in our laboratory (Great Lakes Orthodontics);technicians frequently break out upon exposure to methyl-methacrylate monomer. Although significantly less frequentfor cured polymers, these reactions can be serious and requirecareful analysis and description. The authors presented a lucidaccounting of their work, which included a good variety oftechniques. I believe a few technical points, unrelated to theirexperimental work, should be mentioned.

When discussing immune reactions, “Hamptons” arehaptens (the English dental lexicon has enough peculiarwords). It is also most unlikely (virtually impossible) fordental acrylic resins to contain formaldehyde; listing formal-dehyde as a primary cutaneous antigen in dental acrylics isabsurd, and this type of statement should not be allowed tocapriciously find its way into the dental literature. Also,benzyl peroxide is not benzoyl peroxide; they are chemicallydistinct. Benzyl peroxide incorrectly appears on the Internetin regard to acne.

Finally, I find it disturbing to advocate overcomingacrylic reactions in sensitive denture patients by intentionallyexposing them to additional acrylic. Should this becomestandard practice? Here, light-cured methylmethacrylate isassumed to be safe—with less residual monomer than heat-cured. The authors also make a point of stating that allergicreactions are not dose-dependent.

The issue of allergic reaction remains valid with theincreasing number of sensitizing agents surrounding us all.Such nice clinical work should be married with an equallycareful analysis.

Mark LaurenDirector, Research and Development

Great Lakes Orthodontics, Tonawanda, NYAm J Orthod Dentofacial Orthop 2006;130:1250889-5406/$32.00Copyright © 2006 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2006.06.006

Author’s responseWe thank Mr Lauren for his interest on our article, in

which we presented a patient with an allergy to auto-polymerized acrylic resin. We especially appreciated theconsiderations on vocabulary, a major drawback when writ-

*The viewpoints expressed are solely those of the author(s) and do not reflect

those of the editor(s), publisher(s), or Association.

ing in a foreign language. Even though there are some casereports of patients who had allergic reactions to auto-poly-merized acrylic resins, dental staff are much more oftenaffected by these allergic reactions than patients, includingalso respiratory and systemic effects.1 Orthodontists shouldbe aware of allergic reactions in patients and be able to workin a multidisciplinary team capable of formulating a cleardiagnosis and pointing out proper alternatives. The patientdiscussed in our article initially showed erythema under heracrylic resin retainer and some systemic involvement, such asdifficulty in swallowing and hypersalivation. She was referredto a dermatologist, who evaluated her for allergenic responses(questionnaire and skin patch test, according to the guidelinesof the International Contact Dermatitis Research Group). Thisapproach is consistent with the literature.2 Patch testing inthese situations is standard practice in Brazil and also in theUnited States, as advocated by the American Academy ofDermatology.3 When performed by a qualified professional ina controlled situation, it is a safe procedure. Eckerman andKanerva4 affirmed that the diagnosis of allergic contactdermatitis caused by methacrylates is based on patch testing.Also, as stated by Koutis and Freeman,5 patients with oralcomplaints especially related to wearing dental appliancesshould be patch-tested with allergens in the acrylate series. Asseen, patch testing is strongly advocated. A vast amount ofliterature is available supporting these authors.5-15

Regarding formaldehyde in acrylic resins, we do agreethat it is not a chemical in methylmethacrylate resins. It is,however, found in controlled experiments, leaching from thecured acrylic.16-18 The dental literature has enough reports, sowe could have avoided that discussion. It is not yet clear howit happens, but the possibility of oxidation of methylmetha-crylate groups into formaldehyde has been considered byTsuchiya et al.17,18 Because formaldehyde has been shown tobe not only allergenic, but also cytotoxic, in the concentra-tions leached from acrylic resins, we understand Mr Lauren’sconcerns as a representative from a dental materials corpora-tion and all that might be involved. We suggest reading thecited articles as a starting point to elucidate this importantmatter.

We believe Mr Lauren misunderstood the brief statementregarding the aspect of dose-dependency. It is clear in the textthat each patient has a different chemical profile, as suggestedby Kusy,19 and the allergic reaction depends on the concen-tration related to each person’s tolerance level. For 1 patient,a small dose can cause an allergic reaction, whereas anotherpatient might have no reaction, as stated in the text, “becausean allergic reaction is not dose-dependent, but related to thepatient’s sensitivity.” As we reported, although there waslittle residual monomer on the patient’s retainer, it wasenough to cause a reaction.

Even though it was not mentioned in our article, Mr

Lauren stated that, in his country, light-cured resin is widely

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