Uncoated specimen of human enamel observed in the scanning electron microscope

A 1-mm-thick section of a human premolar was acid etched and observed uncoated in the SEM at accelerating voltages of 3, 5, 10 and 15 kV. Prisms and interprismatic substance were easily distinguishable. Low-voltage operation (3 and 5 kV) gave the best results. Specimen charging was detectable at 5 kV and caused reduced image quality at 10 and 15 kV. Application of silver paste did not reduce charging appreciably. Prolonged observation at high magnification (x 10 000) resulted in contamination of the specimen with consequent charging and reduced resolution. Dental enamel seems to be a material which is well suited when uncoated for observation in the SEM. This may be due both to the high content of the relatively heavy atom calcium, giving good secondary electron emission, and possibly to a certain degree of conductivity caused by diffusible ions.