Value of epicutaneous patch testing in patients with oral, mucosal lesions of lichenoid character

The purpose of the present investigation was to determine, in patients with oral mucosal lesions of lichenoid character, whether it is possible with epicutaneous patch tests, to detect those who will react favorably to removal of amalgam. Of 48 patients, 19 (39.6%) showed positive patch test reactions to 1% mercury ammonium chloride, and 29 (60.4%) showed negative test results. The observation period varied from 3 months to 3 yr (mean value 1.5 yr). After treatment, 94.7% of the positive group and 86.2% of the negative group showed regression of lesions. Reactions exceeding the contact zone between amalgam restorations and lesions showed positive patch test results in 21% of the cases, as compared with 47% among those with lesions restricted to the contact areas; 85.7 and 93.9%, respectively, showed regression after removal of amalgam restorations. The results of the present study indicate that removal of amalgam usually affects the lesions favorably and that epicutaneous patch tests are of little prognostic value in patients with oral mucosal lesions of lichenoid character.