Effectiveness of gutta-percha removal with and without the microscope

The microscope may be useful in retreatment to enhance removal of gutta-percha (GP) and to identify deficiencies in the original treatment. This study compared the effectiveness of GP removal with and without a microscope. Forty-five extracted canines were stepback prepared and obturated with GP and Roth's sealer using lateral condensation. Teeth were stored for 17 months in a humidor, then divided into four groups: group 1 (n = 20)-GP removal without aid of the microscope (group 1 criteria for GP removal was lack of GP on final files and on paper points agitated within the chloroform-filled canal); group 2 (n = 20)-GP removal with the microscope. (In addition to group 1 criteria, canals were inspected with the microscope; additional GP was removed when identified. In both groups, GP was removed using a combination of mechanical instrumentation, chloroform solvent, and K-files); group 3 (n = 3)-positive control, canals remained obturated; and group 4 (n = 2)- negative control, canals were neither prepared nor obturated. Teeth were split longitudinally, photographed, then divided into thirds to compare the apical, middle, and cervical thirds. Remnants of GP and sealer on the canal wall were traced with a digitizer, and the remaining mean % GP was analyzed by t test. Group 1 had 8.3% remaining GP, and group 2 had 7.3% remaining GP. There was no significant difference demonstrated between the two experimental groups.