No changes were found in the epithelial cells from the buccal mucosa of dentists with the use of the light microscope, electron microscope, or electron probe that could be correlated with mercury exposure under the conditions of this test. In a normal population it can be expected that at least 0.01% of the population will show class 2 atypical smears. Patients with class 2 smears have fewer highly matured epithelial cells (tendency toward keratinization) of the buccal mucosa and hence a thinner epithelium.