Removal of Filling Materials from Oval-shaped Canals Using Laser Irradiation: A Micro–computed Tomographic Study

• We examined the efficacy of 3 lasers in removing filling remnants after retreatment with rotary files.
• Forty-two mandibular canine teeth were used.
• We examined the percentage volume of the remaining filling material.
• None of the retreatment procedures completely removed the filling materials.
• The additional use of the lasers improved the removal of filling materials.

IntroductionThe aim of this study was to assess the efficacy of lasers in removing filling remnants from oval-shaped canals after retreatment procedures with rotary instruments using micro–computed tomographic imaging.MethodsThe root canals of 42 mandibular canines were prepared and obturated using the warm vertical compaction technique. Retreatment was performed with rotary instruments, and the specimens were distributed in 3 groups (n = 14) according to the laser device used in a later stage of retreatment procedure: Er:YAG, Er:YAG laser–based photon-induced photoacoustic streaming, and Nd:YAG. The specimens were scanned in a micro–computed tomographic device after root canal filling and each stage of retreatment at a resolution of 13.68 μm. The percentage differences of the remaining filling material before and after laser application within and between groups were statistically compared using the paired sample t test and 1-way analysis of variance test, respectively. Significance level was set at 5%.ResultsOverall, filling residues were located mainly in the apical third and into canal irregularities after the retreatment procedures. After using rotary instruments, the mean percentage volume of the filling remnants ranged from 13%–16%, with no statistical significant difference between groups (P > .05). Within groups, additional laser application had a significant reduction in the amount of the remaining filling materials (P < .05). A comparison between groups showed that Er:YAG laser application after the use of rotary instruments had a significantly higher removal of filling remnants (∼13%) than Er:YAG laser–based photon-induced photoacoustic streaming (∼4%) and Nd:YAG (∼3%) (P < .05).ConclusionsNone of the retreatment procedures completely removed the filling materials. The additional use of lasers improved the removal of filling material after the retreatment procedure with rotary instruments.