X smart

Participants began by watching an instructional video explaining how the Race Evo system is used. They were also given the manufacturer’s brochure, which indicated the instruments' sequence: First, a hand #15 K file is taken to full working length, then Race Evo rotary instrument size 15/taper 0.04, followed by size 25/taper 0.04, and size 30/taper 0.04 [19 ]. The Race Evo rotary instruments were used on an electric motor (X-smart, Dentsply–Sirona, Charlotte NC; USA) according to manufacturer’s instructions. Each rotary instrument was used with gentle 2–3 mm strokes concomitant with light apical pressure that allows the instrument to advance passively within the canal, until working length is reached. After three strokes the file is removed, cleaned and canal irrigation and recapitulation were performed.
All instruments were lubricated with EDTA gel during canal preparation, and warm water was used for rinsing after each file. Fractured instruments were replaced with new instruments, otherwise the same set of instruments was used to instrument the three canals. The time required for complete instrumentation of each canal (including irrigation and instrument change) was recorded.

Root canals were prepared with PTU instruments which were used at 300 rpm with 2 Ncm torque with a torque controlled endodontic motor (X-Smart, Dentsply Maillefer, Konstanz, Switzerland). An SX file was used at one-half of the WL, S1 and S2 files were used at two-thirds of the WL, and F1 (20/0.07), F2 (25/0.08), F3 (30/0.06), and F4 (40/0.06) files were used at full WL. SX, S1, and S2 were used with brushing motion meanwhile other files were used with a gentle in-and-out motion. Irrigation was performed after every file with distilled water with open ended needle.

In both the groups, instrumentation was done according to manufacturer's instructions using a new file for every tooth in both the groups. 2.5% sodium hypochlorite was used as an irrigant and Glyde (Dentsply Maillefer) as a lubricant.
In the PT group, using an electric motor (X-Smart; Dentsply Maillefer) with a 16:1 reduction handpiece, a new set of rotary S1-F2 instruments was used in a sequence to prepare each sample.
Each sample in the SAF group was prepared using a new 21 mm/1.5 mm SAF file attached to an EndoStation endodontic motor and RDT3 handpiece (ReDent Nova) operating at a frequency of 5000 oscillations per minute and amplitude of 0.4 mm. A continuous short pecking motion was used for 4 min while maintaining the irrigant flow rate at 4 mL/min.

Airborne bacterial contamination was prevented with aseptic techniques in a Class I laminar airflow cabinet. All rotary systems were used with torque-controlled endodontic motors (X-Smart, Dentsply Maillefer). The automatic reverse function mode was used except with the TFA. The instrumentation sequences were used with gentle and minimal pressure as follows:

WOG Primary file (size 25, 0.08 taper) was used for root canal instrumentation procedure in a reciprocating working motion at 300 rpm with a proprietary motor (X-Smart, Dentsply Maillefer).