Influence of entrapped air on the accuracy of leakage studies using dye penetration methods

Entrapped air can inhibit dye penetration resulting in failure to demonstrate existing voids. A new approach to study dye penetration was developed in which the entrapped air was evacuated before the dye was introduced. This method was compared with the regular technique of passive dye diffusion. Uniformly prepared root canal specimens were filled with AH26. Two different sizes of standardized voids were created in the specimens. Specimens were either immersed passively in 2% methylene blue for a week or placed in a chamber with 100 mtorr absolute pressure, after which the dye was introduced while the vacuum was maintained. Leakage was measured stereomicroscopically. Controls with no voids showed insignificant external leakage. Passive dye penetration resulted in incomplete filling of the voids regardless of size of the voids, whereas vacuum dye delivery resulted in complete filling of the voids. Results of this study suggest that entrapped air produces artifacts in passive immersion technique; therefore, the sample should be evacuated prior to the dye introduction in order to demonstrate the full extent of void in future dye penetration studies.