Protaper

The specimens were removed from their models, and the
endodontic access cavities were prepared. The pulp tissues
were removed using barbed broaches. After controlling the
patency with the #8 K-File (Dentsply Maillefer), coronal flaring
was performed using SX rotary files (ProTaper, Dentsply
Maillefer, Ballaigues, Switzerland) to gain straight-line access.
The actual root canal lengths were determined by a
different blinded investigator, by inserting the 10 K-file into the root canal until the file tip became visible at the apical
foramen under 4x magnification using an operating microscope
(Leica Microsystems, Wetzlar, Germany). The rubber
stop was placed at the predefined coronal reference point,
and the actual root canal length was measured using an
electronic digital caliper with a resolution of 0.01 mm (Allendale
Electronics Ltd, New Scotland, Canada). After repeating
the measurements, the average of two measurements was
recorded as the actual root canal length.

The root canals were prepared with the ProTaper (Dentsply, Maillefer, Switzerland) rotary file system till size F3 according to manufacturer's instructions in a crown down manner. During biomechanical preparation, the canals were irrigated with 2 ml of 1% sodium hypochlorite solution after each instrument change. This procedure was followed by irrigation with saline solution.

The teeth were embedded rigidly in an 0.2% agarose gel containing 1 mL 0.1% cresol purple (Titan Media) in clear plastic containers. A size #15K file (Dentsply) was placed at the WL in canal to prevent the agarose gel from getting into the canals. Hundred anterior teeth were randomly divided into six groups as follows:

Group I – NI (n = 20)

Group II – PUI (n = 20)

Group III – PSI (n = 20)

Group IV – NP (n = 20)

Group V – positive control (n = 10)

Group VI – negative control (n = 10).

Chemomechanical preparation was done with the Crown-Down technique using rotary ProTaper (Dentsply Maillefer) system till F3. Apical patency was maintained by passing a #15 K file to the WL after each rotary instrument. In all groups, 12 ml of 3% NaOCl was delivered for 180 s [Figure 1].

Forty human maxillary second premolars with similar root lengths, fully formed apices, and without caries, cracks, or previous endodontic treatments were selected. Teeth were stored in 0.2% thymol solution at room temperature for 6 months and external debris was removed using a hand scaler. The coronal part of each tooth was sectioned 1 mm below the cementoenamel junction with diamond disks (Ref. 070, D&Z, Berlin, Germany) to achieve a uniform length of 15 mm. Root canals were prepared to a working length of 1 mm from the apex by using the crown-down technique with rotary instruments (size S1 to F3, Pro-Taper, Dentsply-Maillefer, Ballaigues, Switzerland) to a size #30 (0.09 taper). Canals were irrigated using 2.5% sodium hypochlorite (AriaDent, Tehran, Iran) and normal saline during the instrumentation. Then canals were dried by absorbent paper points (AriaDent) and filled using a cold lateral condensation technique with the same size Protaper gutta-percha points (Suredent, Seongnam, South Korea) and resin-based endodontic sealer AH26 (Dentsply DeTrey GmbH, Konstanz, Germany). The endodontically treated teeth were sealed with glass ionomer restorative material (Vitremer, 3M ESPE, St Paul, MN, USA) and stored in water at 37℃ for 1 week to allow the endodontic sealer to set.

Eighty freshly extracted single rooted premolar with mature apex were used in this study. After access opening for all teeth the WL was determined by placing #10 K file with a rubber stop carefully inserted into each canal until it was just visible in the apical foramen, this length was noted and 1 mm was subtracted to give the WL of the canal and all the selected teeth WL corrected to 19 mm. The teeth were prepared with Protaper (Dentsply, Maillefer) hand system in crown-down approach, and the instruments were used according to the manufacturer's instructions. The apical enlargement was done to size F3 (D0 = 30) 8. In each group, 30 s irrigation 9 with 4 ml of normal saline was used after each file with total irrigation time of 120 s. After canal preparation, a method of Myers and Montgomery10 was followed, the apex of teeth were forced through a precut hole in a rubber stopper, then placed on the glass shell vials. A 27G needle was placed through the stopper into the flask to equalize the air pressure inside and outside the vial. In this study, we used open-end needle gauge 23 and double side-vented needle gauge 23 with disposable syringe and open-end needle gauge 23 and double side-vented needle gauge attached to (Aqua-pick 300) which produced water jet with 100 psi pressure and with 1800 pulsations per minute on its end and fix them by a glue to used it inside canal.