Laser-activated vs ultrasonic-activated techniques for the r
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Tricalcium silicate-based sealers have been usually indicated for the single-cone technique and result in more residual filling materials in root canal retreatment. Passive ultrasonic irrigation and photon-initiated photoacoustic streaming have been reported to improve the removal efficacy of root canal filling materials.

The aim of this study was to evaluate the efficacy of laser-activated and ultrasonic-activated techniques in vitro for the removal of the tricalcium silicate-based sealer iRoot SP and gutta-percha after standard canal retreatment procedures with the use of nickel-titanium (NiTi) rotary instruments.

36 extracted single-rooted teeth were filled using a single-cone technique with GP and iRoot SP sealer. These root canals were then retreated using the ProTaper Universal retreatment (PTUR) system. The samples were divided into three groups according to the final irrigation techniques used in retreatment procedures:
group 1, classic syringe-based irrigation (CSI);
group 2, passive ultrasonic irrigation (PUI);
and group 3, photon-initiated photoacoustic streaming (PIPS).

All groups were irrigated with 2.5% sodium hypochlorite and 17% EDTA solutions. Micro-CT scans were taken to evaluate the volume of root filling materials. The cleanliness of root canal walls was scored by scanning electron microscopy (SEM).

All groups had residual root filling materials in the root canals after mechanical retreatment. Additional use of PIPS removed a significantly higher volume of root fillings than PUI and CSI techniques. SEM scores were significantly lower in the PIPS group than in the PUI and CSI groups, especially in the middle and apical thirds.

None of the additional techniques in this study completely removed the residual iRoot SP and gutta-percha. Compared to PUI and CSI, activation of 2.5% sodium hypochlorite and 17% EDTA with PIPS greatly improved the removal of the residual iRoot SP and gutta-percha following NiTi mechanical retreatment.

BMC Oral Health