Comparative study of retreatment of Thermafil and lateral condensation endodontic fillings

The aim of the present study was to evaluate the possibility of retreating teeth obturated with: (i) Thermafil with plastic carrier, (ii) Thermafil with metallic carrier and (iii) laterally condensed gutta-percha. The following aspects were analysed: removal of obturation, time required for removal, remaining filling material and apical extrusion during reinstrumentation. Thirty human teeth with a single canal were instrumented up to a size 45 K-type file, divided into three groups of 10 teeth each and obturated with Thermafil with plastic carrier (group 1), Thermafil with metallic carrier (group 2), and laterally condensed gutta-percha (group 3) with AH26 as the sealer. Reinstrumentation was performed manually after 30 days storage using Hedstroem files and xylene as a solvent. The average time needed to remove the obturation was 12 min 1 s for group 1, 14 min 36 s for group 2 and 11 min 26 s for group 3. Although no statistically significant differences were observed between groups 1 and 2, and 1 and 3 (P > 0.05), the differences between groups 2 and 3 were significant (P < 0.05). The amount of remaining filling material was significantly higher in group 2 when compared with groups 1 and 2 (P < 0.01). Although the lowest incidence of apical extrusion during reinstrumentation was found in group 3, the differences among groups were not statistically significant.