Patch test reactions to metal salts in patients with oral mucosal lesions associated with amalgam restorations

Patch testing with various metal salts was performed in patients with oral mucosal lesions associated with amalgam restorations, by using polypropylene-coated aluminium discs. Positive reactions to mercuric chloride were obtained in 5/12 (42%) of these patients, but only in 1/11 patients (9%) with oral mucosal lesions unassociated with amalgam restorations and in 3/36 patients (8%) in a control group without mucosal lesions. The difference between the former group and the control patients is statistically significant (p less than 0.05). In addition, a positive test reaction to copper sulfate was obtained in 2 patients (16%) with amalgam-associated mucosal lesions and negative reactions to mercuric chloride. 2 of the 5 positive test reactions to mercuric chloride, in the patients with lichenoid mucosal lesions associated with amalgam, became lichenoid and persisted for at least 3 weeks. The patients with these reactions were also positive at a concentration of 0.05% mercuric chloride, but were negative to metallic mercury, in contrast to 2 other patients in the same group. This indicates the necessity of including mercuric chloride when patch testing such patients.