X smart motor

The bending resistance of the instruments (N = 20/brand) were assessed by a cantilever-bending test as previously reported.¹⁹ (link)^,20 (link) Each file was inserted into the contra-angle of an endodontic motor (X-smart motor, Dentsply Maillefer) that was mounted vertically in a universal testing machine (AGS-X STD, Shimadzu, Kyoto, Japan) with vinyl poly-siloxane impression material (Fig. 1a). The file shank was then inserted into a standardized groove that had been prepared in a heat-resistant plastic container and submerged in distilled water (DW) (Fig. 1b). DW temperatures were either 22 ± 1 °C (RT, N = 10/brand) or 37 ± 1 °C (BT, N = 10/brand). The load cell was 20 N, and the cross-head speed was 2 mm/min. Load was applied at a point 3 mm from the tip of the NiTi file using a stainless-steel blade, which was connected to the crosshead of the universal testing machine (AGS-X STD, Shimadzu). When the blade was depressed 3 mm, the stress was recorded to evaluate the bending resistance.Figure 1

Apparatus used for the bending resistance test (a, b) and the cyclic fatigue fracture test (c, d, e). The angle and radius of curvature of the artificial canal is depicted in (e).

Figure 1

The canals were localized and explored with #10 K-file (Dentsply Maillefer). The working length (WL) was determined by inserting a #10 K-file to the root canal terminus and subtracting 0.5 mm from this measurement under 8× magnification of a surgical microscope. The buccal and lingual canals in each mesial root were randomly assigned to WO or PTN group.
In the WO group, the primary file #25/0.08 was used in a programmed reciprocating motion generated by the X-Smart motor (Dentsply Maillefer) in the “WaveOne” mode. File was used in a slow in-and-out pecking motion (amplitude less than 3 mm, 3 pecks) according to the manufacture's instruction. The flutes of the instruments were cleaned after 3 pecks.
In the PTN group, PTN instruments were used in a crown-down fashion with brushing motion at a speed of 300 rpm generated by the X-Smart motor. The ProTaper Universal SX was used to enlarge the coronal aspect of the canal. This was followed by using the X1 to full WL, and canal finishing was performed with the X2 to full WL.
Apical patency was checked with a size #15 K-file between two instruments. Before the use, each instrument was lubricated with Glyde (Dentsply Maillefer). Irrigation was performed with copious 5.25% NaOCl after the use of each file and when root canal instrumentation was complete.

Root canal instrumentation was performed up to finishing file F4 in a sequence according to the manufacturer's guidelines. The ProTaper universal instruments were driven at 300 rpm with 2N/cm of torque using an X-Smart Motor (Dentsply, Maillefer, Ballaigues, Switzerland).

A K-file # 10 (Dentsply Maillefer, Switzerland) was introduced into each canal until it was visualized through the apical foramen and the length was determined. Working length (WL) was estimated by 0.5 mm from that length. The apical end was sealed with a nail polish. Canal preparation was completed using the ProTaper Universal system (Dentsply-Maillefer, Ballaigues, Switzerland) up to a master apical file # F4 connected to an X-Smart motor (Dentsply-Maillefer, Ballaigues, Switzerland) at 250 rpm and a torque setting of up to 2.5 N/cm. Firstly, SX and S1 were used to 2/3 of WL to flare the coronal and middle 2/3. Later, rotary instrumentation was accomplished using S1, S2, F1, F2, F3 and F4 (size 40/ 0.06 taper) to WL. Between each file change, instrumentation was performed with intermittent irrigation with 5.25% NaOCl for 1 min. followed by sterile distilled water using side vented needle with a 30 gauge (Dentsply Rinn, Elgin, II). Final irrigation was ended using 5 ml of 17% ethylene diamine tetra acetic acid (EDTA) (MD-Cleanser, META-BIOMED, Korea) for 1 min. followed by 5ml of distilled water.