Table 1 Study groups

I

Chemomechanical preparation with a rotary motion by using Profile 04 system files (Dentsply-Maillefer) driven by the X-Smart Plus electric motor (Dentsply-Maillefer) at 300 rpm with a torque setting of 2 N.cm, with a slow in-and-out pecking motion that did not exceed 3–4 mm in amplitude, according to the crown-down philosophy without IFE, i.e., the apical limit was established around the AC (-0.5 mm from the AF identified by the apex locator^a as 0.0 mm). A 2.5 mL aliquot of 2.5% NaOCl was used as an irrigating solution at each file use or change, applied with a NaviTip 31 G needle (Ultradent) up to 5 mm short of the AF. The same amount of NaOCl was used for each canal (40 mL)

II

The exact specifications described for Group I, but with IFE, i.e., the apical limit was established at 0.5 mm beyond the AF (identified by the apex locator^a as 0.0 mm)

III

Chemomechanical preparation with a reciprocating motion by using Reciproc system files (VDW) driven by the X-Smart Plus electric motor (Dentsply-Maillefer), with a slow in-and-out pecking motion that did not exceed 3–4 mm in amplitude without IFE, i.e., the apical limit was established around the AC (-0.5 mm from the AF identified by the apex locator^a as 0.0 mm). A 2.5 mL aliquot of 2.5% NaOCl was used as an irrigating solution at each file use or change, applied with a NaviTip 31 G needle (Ultradent) up to 5 mm short of the AF. The same amount of NaOCl was used for each canal (40 mL)

IV

The exact specifications described for Group III, but with IFE, i.e., the apical limit was established at 0.5 mm beyond the AF (identified by the apex locator^a as 0.0 mm)