Reliability of reduced air pressure methods used to assess the apical seal

The reliability of two commonly used methods of sealability testing, dye leakage under normal atmospheric pressure and dye leakage in a partial vacuum, was tested using a repeated studies design. Forty extracted teeth were instrumented and obturated using lateral condensation of gutta-percha and Sealapex sealer. One-half of the teeth were placed in India ink under normal atmospheric pressure and the other half underwent air evacuation before immersion in the ink. After 24 h the teeth were removed from the ink and rendered transparent for linear leakage analysis. A second study, repeated within the exact parameters of the first, was performed approximately 1 month later. Mann-Whitney U tests indicated that there was no significant difference (P>0.05) between the air and vacuum groups or within each group (air or vacuum) between trials, indicating that the methodology is repeatable and that application of reduced air pressure did not enhance reliability. A large majority of the teeth placed under partial vacuum showed evidence of vacuum-induced artefacts that may negate the value of vacuum as a research tool.