Accuracy of endodontic microleakage results: autoradiographic vs. volumetric measurements

The correlation between autoradiographic and volumetric leakage measurements was evaluated. Seventy-two anterior teeth with a single canal were selected and divided into three groups of 24. Group 1 served as control (no obturation), group 2 was obturated with gutta-percha only, and group 3 was obturated with gutta-percha and endodontic sealer. Samples were placed in a vertical position in 48-well cell culture plates and immersed in 1 ml of [14C]urea for 14 days. One-mm-thick horizontal serial sections were cut with a diamond disk cooled with liquid-nitrogen gas. Linear penetration was recorded by five independent evaluators from autoradiographs. Volumetric results were based on counts per minute registered in a liquid scintillation spectrometer. Pearson's correlation coefficient test was used to determine the lineal correlation between both methods of evaluation. No acceptable correlation values were found in any of the three groups (group 1, r = 0.34; group 2, r = 0.23; group 3, r = 0.20). Our results indicate that there is no correlation between linear and volumetric measurements of leakage.