Oral lichen planus: hypersensitivity to dental restoration material.

67 patients with oral lichen planus of the atrophic-erosive or reticular plaque type were examined. Dental amalgam in contact with mucosal lesions was present in 64 patients, and gold fillings in 33. Patch testing with a standard procedure was performed with components of dental fillings. 11 patients (16%) reacted to at least one of the mercury compounds compared to 8% in a reference group. Most positive reactions were caused by elemental mercury and ammoniated mercury. No patient reacted to gold or copper. Readings at days 10-14 did not increase the number of responders. 13 patients were patch tested with palladium; all were negative. It is not clear whether in the mercury-positive patients allergy to dental amalgam is a causative or aggravating factor, or merely on epiphenomenon.