Supplementary instrumentation did not enhance the removal of residual gutta-percha: a micro-computed tomography study

We evaluated the effect of supplementary instrumentation on the removal of gutta-percha and compared the efficacy of three file systems with different metallurgical properties via micro-computed tomography (micro-CT). Forty-two moderately curved mandibular molars were selected and divided into 3 groups (n = 14): group-PTG: ProTaper Gold, group-PTN: ProTaper Next, and group-VB: Vortex Blue. Only mesial roots with Vertucci type-IV configuration were included. Canals were instrumented and obturated with bioceramic sealer. Retreatment was performed using a retreatment file system, and supplementary instrumentation was completed according to experimental groups: ProTaper Next X4 (40/06), ProTaper Gold 40/06, and Vortex Blue 40/06. Initial, second (after using the retreatment file system), and final (after supplementary instrumentation) micro-CTs were obtained (resolution 85 kV, 118 µA, and 13.6 µA pixel size), and residual gutta-percha at apical, middle, and coronal thirds was calculated. One-way ANOVA and Student's t test were performed for statistical analysis. While the first and second micro-CT values demonstrated a statistical difference (p < 0.05), there was no difference between the second and final micro-CT values. No differences were detected between group-PTN (96.89-98.32%), group-PTG (95.36-98.51%), and group-VB (%96.96-%99.38). Residual gutta-percha volumes were similar in mesiobuccal and mesiolingual canals. Supplementary instrumentation did not decrease the amount of residual gutta-percha. Increasing the initial apical size by three sizes removed 98.18% to 99.38% of gutta-percha. ProTaper Next, ProTaper Gold, and Vortex Blue showed similar effects. In the apical third of mesiobuccal, ProTaper Gold and Vortex Blue eliminated gutta-percha more effectively than ProTaper Next.