The effect of the apical dentinal plug on broken endodontic instruments

This study was concerned with the leakage that occurs around broken endodontic instruments when they are left in the apical third of the root canal. Dissociated single-rooted human teeth were used after the crowns were removed. One hundred specimens were prepared by filing and filling according to accepted clinical standards, except that various sizes and styles of instrument segments were intentionally left in the apical third of the canals of 70 specimens. Leakage of these specimens was evaluated by placing them in Ca 45 solution, sectioning, and making auto radiograms. Variations in style and size of instruments did not affect the results, but the presence of dentinal debris was highly significant to the leakage results. The scanning electron microscope, was used to investigate the nature of the dentinal debris and how it physically related to the file fragments and dentinal walls. The scanning electron microscope showed that the dentinal debris was not produced by sectioning the segments because the debris was not seen in the canals that were known to be patent.