Thus, the aim of this in vitro study was to evaluate the effects of three dissolving agents on the accuracy of an EAL and endodontic handpiece combined device during an orthograde retreatment procedure.2. Materials and Methods2.1. Sample PreparationIn total, 56 freshly extracted human maxillary high throughput screening incisor teeth, stored in saline, were used. The teeth were evaluated by obtaining mesiodistal and buccolingual radiographs and an operating microscope at ��10 magnification (Opmi Pico, Carl Zeiss, Germany) to determine that they had noncomplicated root canal anatomy, mature root formation, and no external root resorption, cracks, or fractures along the roots. All crowns were cut at the cementoenamel junction with a diamond disc to simplify access to the root canal and to provide a stable reference for all measurements.

Root canal patency was controlled with a size 10K-file (Mani Inc., Tochigi-Ken, Japan) in each root.2.2. Assessment of the True LengthThe true length (TL) was measured visually with the help of an operating microscope at ��10 magnification, as described by Thomas et al. [11]. A size 10 stainless steel file (VDW, Antaeos, Munich, Germany) was placed into the root canal until the tip of the file reached the plane of the major foramen. The distance between the file tip and the stopper was measured with digital callipers (��0.01mm accuracy). The measurements were repeated three times, and the average was taken as the raw length (RL). Then, 0.5mm was subtracted from the RL measurements, and the calculated value was recorded as the TL.2.3.

Preparation of Root CanalsEach root was prepared using the ProTaper System (Dentsply, Maillefer, Ballaigues, Switzerland) to TL. S1, S2, F1, and F2 files were used, according to the manufacturer’s recommendations, with an endodontic motor (X-Smart, Dentsply). The master apical file (MAF) was F2 for all roots. The root canals were irrigated with 2.5% NaOCl after each change of instrument. For the final irrigation, 3mL of 17% EDTA was used for 1min, followed by 3mL of 2.5% NaOCl and 3mL of distilled water. The root canals were then dried with paper points. The roots were randomly divided into two experimental groups (n = 20 each) and a control group (n = 16; Table 1).Table 1The distribution of all experimental groups according to the materials used and the percentages of accuracy at ��0.5 and ��1.

0mm of all groups for ARL and EL modes according to true length (TL).2.4. Penetration of Root Fillings and Assessment of Electronic Working Lengths (ARL and EL)In the present study, two evaluations were performed for the Tri Auto ZX device. The first was the apical accuracy during the autoreverse function (��ARL��), and the second was only the apical accuracy during the EAL function (��EL��).2.4.1. Group A Twenty roots were filled with lateral compaction using a size F2 master gutta-percha cone (Dentsply) and an epoxy resin-based GSK-3 (AH Plus, Dentsply DeTrey, Konstanz, Germany) root canal sealer.