Comparative analysis of mechanical properties of differently tapered nickeltitanium endodontic rotary instruments

Abstract

This study aimed to compare the mechanical properties of differently-tapered EndoWave nickel-titanium endodontic rotary instruments (size #30/0.04 taper and #30/0.06 taper; Group 0.04 and 0.06, respectively). Torsional and bending properties were evaluated with the cyclic fatigue test and the cantilever bending test, respectively. Canal transportation was assessed following instrumentation of curved canals in resin blocks. Torque and apical force during instrumentation were determined using an automated instrumentation and torque/force analyzing device. The number of cycles to fracture was Group 0.04>Group 0.06 (p<0.05). The bending load values were Group 0.06>Group 0.04 (p<0.05). Group 0.04 better maintained the original canal shape compared with Group 0.06. The median clockwise torque value was Group 0.06>Group 0.04 (p<0.05), whereas no significant differences were detected in the median counterclockwise torque and apical force values (p>0.05). Under the present experimental condition, 0.04- and 0.06-tapered EndoWave instruments exhibited different mechanical properties.

Bending, buckling and torsional resistance of rotary and reciprocating glide path instruments

“…Previous studies have demonstrated that the larger the crosssectional design, the lower the flexibility of an instrument (Nakagawa et al 2014, Fukumori et al 2018. Further, the instrument's taper also influences its flexibility (Nakagawa et al 2014, Fukumori et al 2018. RP, PG and WOGG have different nominal sizes and tapers, and this might be considered a limitation to interpret the results clearly, as these variables cannot be fully isolated.…”

“…The parallelogram (of WOGG) and quadrangular (of PG) cross-sections have larger crosssectional area than S-shaped design (of RP). Previous studies have demonstrated that the larger the crosssectional design, the lower the flexibility of an instrument (Nakagawa et al 2014, Fukumori et al 2018. Further, the instrument's taper also influences its flexibility (Nakagawa et al 2014, Fukumori et al 2018.…”

Enhanced root canal-centering ability and reduced screw-in force generation of reciprocating nickel-titanium instruments with a post-machining thermal treatment

“…An original device described in our previous articles [19][20][21][22] was used with a few modifications. The device consists of an endodontic motor (X-Smart Plus, Dentsply Sirona, Ballaigues, Switzerland), a motorized test stand (MX2-500N, Imada, Aichi, Japan), and a torque/force measuring unit.…”

Relation between laboratory cantilever bending test and finite element analysis of five different nickel-titanium rotary instruments

“…Using a flexible NiTi rotary instruments permits their bending ability inside curved canals with minimal load creation. Moreover, it influences the possibility of endodontic file separation (Fukumori et al 2018). Modifications of the flexibility of the NiTi endodontic rotary instruments depend greatly on their metallurgical composition, fabrication procedure, manufacturing treatment, and geometrical design (He and Ni 2010;Hamdy et al 2019;Galal and Hamdy 2020).…”

“…Modifications of the flexibility of the NiTi endodontic rotary instruments depend greatly on their metallurgical composition, fabrication procedure, manufacturing treatment, and geometrical design (He and Ni 2010;Hamdy et al 2019;Galal and Hamdy 2020). Cantilever bending test is the most frequently used test to evaluate the flexibility of the endodontic rotary instruments (Fukumori et al 2018). The mechanical properties are diverse among the different types of NiTi rotary instruments (Arbab-Chirani et al 2011).…”