2.2. Root Canal Preparation and Activation Procedures
CAVITY, SMEAR LAYER
After access cavity preparation, root canals were prepared using TruNatomy prime shaping files to form root canal systems into a constantly tapering preparation with the most peri-cervical dentin preservation possible.The canals were irrigated with 3 mL of 3% NaOCl and 3 mL of 17% EDTA alternately without activation. Subsequently, every root canal was irrigated with 10mL of distilled water to avoid the prolonged effect of EDTA and NaOCl solutions. Final irrigation of 5 mL of 17% EDTA of the root canal was done to eliminate the smear layer. Then teeth were randomly divided into four laser groups and one control group (n = 13).The final EDTA irrigants in all laser groups were activated using an Er:YAG laser of 2940 nm (Fidelis, Fotona, Ljubljana, Slovenia) following the free-running emission mode, and with a fiber-optic endodontic handpiece at panel settings of 1 W, 20 Hz, and 50 mJ; each using a different tip design and time duration.Laser 1 group = Final irrigant was activated by Preciso/flat laser tip (Fidelis, Fotona, Ljubljana, Slovenia) for 10 s.Laser 2 group = Final irrigant was activated by Xplus tapered laser tip (Fidelis, Fotona, Ljubljana, Slovenia) for 10 s.Laser 3 group = Final irrigant was activated by Preciso/flat laser tip (Fidelis, Fotona, Ljubljana, Slovenia) for 20 s.Laser 4 group = Final irrigant was activated by Xplus tapered laser tip (Fidelis, Fotona, Ljubljana, Slovenia) for 20 s.Control group = The final EDTA irrigants were activated using an ultrasonic tip (IrriS-afe™, Acteon, Merignac, France) for a total time of 60 s (20 s × 3 cycles).The laser tip was placed 12 mm away from the apex and was kept stationary with no advance into the canal in all laser samples. Irrigation with saline was achieved between every two cycles.