Radiopacity of endodontic sealers: development of a new method for direct measurement

Radiopacity is an essential attribute of endodontic filling materials. It is important to see clearly the root canal filling to detect its presence, extent, and apparent condensation. National and international standards require a minimal radiopacity equivalent to 3 or 4 mm of aluminum, yet some products made by reputed companies do not meet this requirement. The result may be unjustified downgrading of clinical cases. The purpose of this investigation was 2-fold: to develop a novel and easily reproducible technique for assessing the radiopacity of endodontic sealers and to apply it to measure the opacity of 21 current cements poured in 6- x 1-mm wells. As in the currently recommended technique, the standardized samples are radiographed alongside an aluminum stepwedge but instead of using an optical densitometer to measure the density and then calculate the radiopacity, the image is digitized. The gray pixel value of the test material is compared with the stepwedge, using computer software, to find the corresponding step. The opacity of the samples ranged from 1.6 mm to more than 11 mm of aluminum. The technique can be advanced to a dry, chemical-less variant by using radiation captors, as for periapical X-rays, instead of film.