Protaper next

Forty single-root mandibular first premolars were selected for this research. All selected teeth were thoroughly cleaned and kept in normal saline and then decorated at the cervical line and adjusted to be the same length of 13 mm with a double-faced diamond disc (Komet Dental, Lemgo, Germany) in constant cool. The working length for the canals was established by inserting an endodontic file size 15 K-type (Dentsply, Switzerland) into the anatomic apex and subtracting (1 mm) from the determined (WL).
All roots were prepared using (Pro Taper Next, Dentsply, Malifer, Switzerland) rotary system to size X3 file and irrigated thoroughly with (2 ml) of sodium-hypochlorite (concentration of 5.25 %) during root canal instrumentation. After that, it was flushed with (10 ml) of distilled water and dried then obturated with size X3 gutta-percha and bioceramic endodontic sealer (Total Fill, FKG Swiss endo, Le Cretdu-Locle Switzerland). The coronal canal openings were sealed with Glass Ionomer Cement (GIC) (Tokuyama, Tokyo, Japan). Finally, the roots were kept for 1 day in a digital incubator at 37 °C and 100 % humidity (Alkhalidi, 2020 (link), Hassoon, 2022 (link)).

Fully erupted, human permanent maxillary anterior teeth, without caries or defects, were collected from local oral surgeons and stored in 10% formalin solution until use (Institutional Review Board#: 010617-005, University of New England, not human subject research). The teeth, extracted for treatment unrelated to this study, were placed under running water for 1 hour, then cleaned for this study with a scaler. Radiographs were taken to exclude teeth with multiple canals, cracks, fractures, resorption, caries, immature apices, or root curvature more than 10°.
Fifteen teeth were selected for NSRCT, and the working length was determined to be 1 mm short of the apex using a size 10 K-file. Canals were cleaned and shaped using ProTaper NEXT (Dentsply Sirona, Johnson City, TN, USA) NiTi rotary files with a ProMark torque-limited electric motor (Dentsply Sirona, Tulsa, OK, USA) to size X5 (#50/variable taper, a 6% taper in a 3 mm tip) using copious 2.5% NaOCl irrigation. The canals were dried by ProTaper NEXT absorbent points (Dentsply Sirona, Johnson City, TN, USA).

The study was conducted at the School of Dental Medicine, University of Zagreb and approved by its Ethics Committee (approval number 05-PA-30-XXII-12/20). The study involved four dentists divided into two age groups:
Each dentist visually assessed the existence of damage to rotating or reciprocal endodontic instruments used in shaping root canals of multirooted teeth. A total of 239 instruments from different manufacturers were estimated by each examiner. The types of instruments evaluated were: Reciproc (VDW Dental, Munich, Germany n = 126), ProTaper Universal (Dentsply Sirona, York, Pennsylvania, USA, n = 59), ProFile (Dentsply Sirona, York, Pennsylvania, USA, n = 15), One curve (Micro mega, Besancon, France, n = 13), ProTaper Next (Dentsply Sirona, York, Pennsylvania, USA, n = 12), ProTaper gold (Dentsply Sirona, York, Pennsylvania, USA, n = 2), HERO shaper (Micro mega, Besancon, France, n = 6), F360 (Komet Dental, Lemgo, Germany, n = 6). The number of times each file had been used was not recorded. The examined instruments were discarded by different operators because of a perceived decrease in cutting efficiency; fracture; or any defects observed by the naked eye, such as unwinding, curving or bending. All files were cleaned by an ultrasonic cleaner and sterilized in an autoclave before inspection.