Ex vivo study of the efficiency of two techniques for the removal of mineral trioxide aggregate used as a root canal filling material

The purpose of this study was to evaluate the removal efficiency of mineral trioxide aggregate (MTA) used as a root filling material. Ninety-three human teeth prepared with a step-back technique were randomly assigned to 2 groups and filled with vertically compacted MTA (group A) or MTA and a gutta-percha cone (group B). Fillings were removed by using ultrasonics and/or rotary nickel-titanium instruments. Roots were split into halves, and a 1 to 4 scoring system was used to assess the amount of residue. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests. Remnants were found in all specimens. Rotary instruments were unable to penetrate canals in group A. The combination of rotary instruments and ultrasonics was superior in group B. Dark discoloration of most MTA fillings was evident. The results suggest that MTA cannot be completely removed from the root canal system by any of the methods examined.