Microleakage associated with retrofilling of the apical two thirds with amalgam

In this investigation the effect of increasing the thickness of amalgam retrofilling on its sealing ability was studied and compared with the sealing ability of the laterally condensed gutta-percha with a sealer. The apical two thirds of the canals of 118 upper central incisors, filled with laterally condensed gutta-percha, were sealed with amalgam. Amalgam retrofills were also used to seal the apices of the roots of six teeth that had no other filling in their canals. The effectiveness of both techniques was determined by their ability to inhibit the penetration of methylene blue dye for the periods of 24 hours, 1 week, and 1, 3, and 6 months. At 24 hours both materials showed comparable sealing ability. However, the sealing ability of laterally condensed gutta-percha was significantly better than that of amalgam from the 1-week period until the end of the study. The depth of marginal penetration around both materials increased with time. The amount of the dye penetration increased acutely around amalgam, whereas its increase around gutta-percha was more uniform. At the end of the study, specimens retrofilled with amalgam exhibited total dye penetration that exceeded the full thickness of amalgam (6 mm) and spread into the root canal space. On the other hand, the mean value for marginal penetration of the dye around the laterally condensed gutta-percha was 2.6 mm at the end of the study. The present investigation proved beyond doubt that the use of any thickness of retrograde amalgam to seal the apex, with no other filling within the canal, invites failure.