Oral lichen planus lesions in contact with amalgam fillings: a clinical, histologic, and immunohistochemical study.

Fifty-one consecutive patients had clinically diagnosed oral lichen planus (OLP) lesions in total or partial contact with amalgam fillings. The clinical features of the OLP lesions were characterized and registered, and biopsies were obtained from each OLP lesion. Histologic and immunohistochemical studies were performed, as well as tests for allergy to dental materials. The clinical diagnosis of OLP corresponded to the World Health Organization (WHO) morphologic OLP criteria in 31 (61%) cases. The remaining lesions were histologically diagnosed as mild OLP in 11 (22%) or as benign oral keratosis in nine (17%) cases. The immunohistochemical examination showed a positive reaction to fibrinogen in the basement membrane zone (BMZ) in 10 (20%) patients and to complement C3 in one (2%) patient. No positive reactions in the BMZ were found for IgA, IgG, and IgM. In 17 (33%) patients, an allergic reaction to mercury was found, and candidiasis was diagnosed in 13 (25%) patients. The true nature of OLP-like lesions in contact with amalgam fillings still remains to be explained. For that matter, we do not know whether OLP is one disease or a number of similar immunologic or other responses to various interacting stimuli. One such stimulus might be mercury from corroding amalgam fillings.