| Summary: | Aim: The cleanliness of dentinal tubules was compared after using different techniques for the removal of root filling material during root canal retreatment with and without solvent. Materials and Methods: Root canals of 90 extracted teeth were prepared and filled in vitro using lateral compaction with gutta-percha and sealer. In the control group (n = 10), the canals were left unfilled. In four experimental groups (n = 20 each), the root fillings were removed after 2 weeks using Hedstrom file, one of two rotary nickel–titanium instruments (ProTaper and Mtwo retreatment files), or a neodymium-doped yttrium aluminum garnet laser with H-file. Each experimental group was further subdivided into two subgroups (n = 10) according to whether the solvent N,N-dimethylformamide was used or not. After final irrigation, the samples were split longitudinally and photographed. The dentinal tubules' cleanliness was evaluated at the microscopic level by a scanning electron microscope in the coronal, middle, and apical thirds of each root half. Results: The number of open tubules was more prevalent in the control group, followed by the nonsolvent subgroups, than in the solvent subgroup (P < 0.05). Conclusions: All of the instruments left some filling materials inside the root canal both with and without solvent, but using solvent led to more remnants inside the dentinal tubules.
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