The effectiveness of a self-adjusting file to remove residual gutta-percha after retreatment with rotary files

Aim To test the efficacy of a two-stage retreatment method in which the Self-Adjusting File (SAF) is used to remove root canal filling residue left in the canal after using ProTaper Universal retreatment files. Method One of the curved mesial canals of 25 extracted mandibular molars was instrumented up to ProTaper F2, followed by NiTi K-files up to size 45 and filled. Radiographs of these canals served as a pre-treatment control, which was later compared with those of the same canals after each stage of the retreatment procedure. Stage 1 consisted of ProTaper Universal D1D3 retreatment files, which were used to remove the bulk of root filling material, followed by stage 2 in which a SAF file was applied to remove the remaining root canal filling residue. The amount of the radiopaque material in each third of the canal was evaluated before and after each stage, using bucco-lingual and mesio-distal radiographs. The amount of residue was expressed as the per cent of the root canal filled area, as measured in the pre-treatment control. The difference between the control and results of the first and second stages of retreatment was analysed using the Wilcoxon signed-rank test. Results Radiopaque residue was present after the use of the ProTaper Universal rotary files in 7.8 (+/- 12.9)%, 12.9 (+/- 13.9)% and 34.7 (+/- 22.8)% of the coronal, mid-root and apical areas, respectively. Following the supplementary application of the SAF, the amounts of residue were reduced to 2.6 (+/- 3.7)%, 4.1 (+/- 5.7)% and 6.7 (+/- 9.4)% of the coronal, mid-root and apical canal areas, respectively (P < 0.01 for the coronal and mid-root and P < 0.001 for the apical third). Conclusion No system removed the root filling materials entirely. The use of the SAF after rotary instrumentation using ProTaper Universal retreatment files resulted in a significant reduction in the amount of filling residue in curved canals of mandibular molars.