Lichenoid reaction associated to amalgam restoration

SEGURA-EGEA JJ, BULLÓN-FERNÁNDEZ P. LICHENOID REACTION ASSOCIATED TO AMALGAM RESTORATION. MED ORAL PATOL ORAL CIR BUCAL 2004;9:421-4.

ABSTRACT

Hypersensitivity to mercury associated with amalgam restorations may occur and present in one of two different ways. Most commonly it presents as an oral lichenoid reaction affecting oral mucosa in direct contact with an amalgam restoration and represents a delayed, type IV, cell mediated immune response to mercury or one of the other constituents of the dental amalgam. We report a case of oral lichenoid reaction associated to amalgam restoration. A 38 year-old woman presented a caries lesion of tooth #37. A Black's class I preparation was performed and filled with amalgam. After 19 months, intra-oral examination revealed atrophic lesion, lightly erythematous, affecting the left buccal mucous. The lesion contacted directly with the amalgam restoration in the lower first molar. The right buccal mucosa was normal. His medical history was unremarkable, he was taking no medication and had no known allergies. However, the patient had felt certain rare sensation in that zone when eating sharp meals. Biopsy showed histological changes compatible with oral lichen planus. The patient decided not to change again the restoration, because she did not have important annoyances and she did not wish to be treated again. Other restorations were performed with composite resins, and no reaction was evidenced in the mucosa.

Key words: Lichenoid reaction, mercury allergy, amalgam toxicity, oral lichen planus.

INTRODUCTION

In the last years, hypersensitivity reactions caused by dental materials, as much in the professionals as in the patients, have been extensively investigated. In the dental environment, substances identified as allergenic include local anaesthetic (1), antibiotics (2), restorative materials (polymethylmethacrylate, resin composites) (3,4), and latex (5). Hypersensitivity to mercury associated with amalgam restorations may also occur (6), and present in one of two different ways. Most commonly it presents as an oral lichenoid reaction affecting oral mucous in direct contact with an amalgam restoration and represents a delayed, type IV, cell mediated immune response to mercury or one of the other constituents of the dental amalgam (7). Much more rarely, an acute generalised or systemic reaction can occur (8). In both cases diagnosis may not be immediately obvious. The oral lichenoid reaction (OLR) is a lesion indistinguishable clinically and histologically of the oral lichen planus (LP). However, OLR disappears when the causing substance is eliminated, generally a drug (antibiotics, antidepressants, antihypertensive, anti-agregants, cardiac glucosides, oral hypoglycaemics, non steroidal anti-inflammatory agents, simpaticomimetics, vasodilators) or dental materials. Most of the lichenoids reactions associated to dental amalgam (97%) disappear after the elimination of the amalgam restoration (9,10). So, it has been recommended to eliminate these restorations when cutaneous lichen planus has not been diagnosed (11). A case of oral lichenoid reaction associated to amalgam restoration in a mandibular molar is reported.

CASE REPORT

A 38 year-old woman was seen for a routine dental examination. Clinical examination disclosed caries decay of tooth # 37 (mandibular left second molar). Her medical and dental history was uneventful. She was not having any drug. She did not show any restoration in his mouth. After intraoral and radiographic examinations, the decayed tooth was treated. A Black's class I preparation was performed and filled with dental amalgam. No postoperative problems were present. After 19 months, patient returned because she suspected the existence of several carious lesions presented in other teeth. 

Intraoral examination disclosed the presence of an atrophic lesion, lightly erythematous, affecting the left jugal mucosa. The lesion contacted directly with the amalgam restoration in the lower first molar (Fig. 1). Right jugal mucosa was normal. His medical history was unremarkable. Patient had not detected the lesion. However, she had felt certain rare sensation in that zone when eating sharp meals. She was having no medication and had no known allergies. Meticulous exploration of the injured zone showed that this one projects on the amalgam restoration, making direct contact during some movements. In fact, it was necessary to separate the mucosa with the mirror to be able to appreciate the lesion.

In order to confirm histologically the nature of the lesion, biopsy was taken. Anathomopathological study revealed (Fig. 2) scamous epithelium, irregular acantosis and centres of paraqueratosis, manifest espongyosis, and the presence of lymphocytes exocytosis in the corneous layer. Underlying stroma showed discreetly lymphocytic chronic inflammatory infiltrated, distributed in band, affecting the basal layer. In depth, fibroconective and adipose tissues with some fine vascular structures, without significant alterations, were observed.Anathomopathological diagnosis was compatible with oral lichen planus. The observed histological feature in mucous was equivalent to acute-subacute dermatitis. Once the nature of the injury was explained to the patient, the patient decided not to change again the restoration, because she did not have important annoyances and she did not wish to be treated again. Other restorations were performed with composite resins, and no reaction was evidenced in the mucous.

DISCUSSION

Although amalgam restorations continue being made frequently in posterior sector, cases of hypersensitivity to dental amalgam are relatively rare. No doubt, OLR is the type of hypersensitivity more frequently described associated to dental amalgam (6,7,9). Essentially this involves a cell mediated, type IV hypersensitivity response to a constituent of the amalgam restoration and as such is the oral equivalent of skin allergic contact dermatitis. Most often the allergen is mercury but occasionally the response is to one of the other components of amalgam alloy such as copper, tin or zinc (6). The lesions of OLR are similar to those of LP. However, they can be distinguished from the lesions of LP by their close relationship with amalgam restorations, and their tendency to be localised and asymmetrically distributed (12). In contrast the lesions of classical LP tend to be more widespread, bilateral and symmetrical in distribution (13). As with LP, OLRs may have reticular, plaque-like, atrophic and erosive components. The case reported here showed an OLR with atypical atrophic LP feature.

Diagnosis of OLR associated to amalgam restoration requires anathomopathological examination, confirmatory in the case reported, and to reject other possible substances as causes of hypersensitivity. In this case, the patient has not other tooth restorations, neither metal-porcelain (14) nor composite resin (4). Moreover, she was not having any type of drug. A positive patch test to mercury or another component of amalgam may help to confirm the diagnosis. Final confirmation, however, may have to await resolution of the lesion following removal of the offending amalgam restoration (11,15).

Patients with OLR contacting with amalgam restorations have more probability of positive patch test to mercury that those with more extensive and not contacting lesions (3). Similarly, the reported benefit of replacing amalgam restorations in patients with LP or OLRs has been variable (15) but has been most effective in those patients with OLR lesions in direct contact with amalgam fillings. In 95% of such patients OLR disappear after removing amalgam restoration.

When the amalgam restoration must to be removed, it always will have to be done using rubber dam, abundant irrigation, and high aspiration volume, to diminish the exposition to the material (6).

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