MODIFIED AUTORADIOGRAPHIC TECHNIQUE FOR MARGINAL PENETRATION STUDIES

Abstract A preliminary investigation has been made in an effort to improve the quality of the autoradiograph for accuracy and interpretation of results in studies of the marginal penetration of radioactive isotopes between filling material and tooth and in studies of the permeability of tooth substance. Photographic glass-plate emulsions provided a more intimate contact with the tooth specimen than did the dental x-ray film. The improved technique uses a composite autoradiograph, localizing the exposure area to the tooth specimen by passing a combination of reflected and transmitted light through the clear photographic glass plate. Under high magnification, black and white or colored photographs can be made and the path and depth of isotope penetration into tooth substance can be more accurately related to the autoradiograph. A 300 micron tooth specimen produced a sharper autoradiograph than a 1 mm. specimen used by other investigators. Serial sections taken from the same test tooth showed different patterns of isotope penetration, raising the question of the reliability of a single-section result. Critical maximal and minimal isotope concentrations and processing times must be predetermined in order to produce a faithful image of the activity in the tooth.