In vitro lymphocyte proliferation test in the diagnosis of oral mucosal hypersensitivity reactions to dental amalgam.

Patch testing was carried out in 23 patients with oral lichenoid lesions (OLL) topographically related to dental amalgam fillings. Twelve patients displayed positive reactions to several mercury compounds, whereas 11 patients were negative. An in vitro lymphocyte proliferation (LyPro) test was carried out using different mercury compounds and other metal salts. Mercuric chloride and phenyl mercuric acetate caused positive proliferation in 3/12 patch test-positive and in 5/11 negative patients. One out of seven healthy control subjects had a positive LyPro result. The mean stimulation index (SI) values between the patient groups or compared with the control subjects did not differ significantly. Zinc, tin, copper or silver salts caused in vitro lymphocyte stimulation in most of the patients and in healthy control people. Total (14) or partial (4) replacement of amalgam fillings was carried out in 18 patients. Complete healing of lichenoid lesions was seen in 4/6 LyPro test-positive and in 5/10 patch test-positive patients at follow-up examinations 12 months after the replacement of amalgam fillings. The in vitro proliferation assay seems not to be a specific test for identifying the patients who would benefit from amalgam replacement.