Background: This study used cone-beam computed tomography (CBCT) to compare a stainless-steel Tornado file system with OneShape and WaveOne rotary systems for biomechanical canal preparation as indicated by the healing of periapical lesions.

Methods: Lower molars with necrotic pulps and periapical lesions were arbitrarily divided into three groups (n=20) rendering to three rotary file systems. After root canal treatment, clinical and radiographic assessment of the apical radiolucency was evaluated at one year using pre- and post-instrumentation CBCT images. Statistical analysis was performed to compare the three systems at a p-value of 0.05.

A sample size of 60 subjects (38 females and 22 males) was randomly selected for this randomized clinical research based on a power of 80%, and a significance level of 0.05. The patients should have lower molars with two separate mesial canals, distinct apical foramen, mature apices, and neither cracks nor resorption. Canal curvature for mesial canals ranged from 15° to 45°. The study excluded patients younger than 16 or older than 65, who had diabetes, immune-compromising conditions, or had previous dental work on the working tooth. We informed the patients about the potential risks, discomfort, and potential benefits. Patients who met the inclusion criteria signed a consent form. Table 1 shows the demographics of the study samples. Every patient was evaluated and reviewed through appropriate history taking, clinical examinations, and pre-operative digital radiography. The past dental and medical history, major complaints, and demographic data were recorded. Operating teeth were scanned with an axial slice thickness of 0.1 mm using a CBCT (Kodak 9000C) with an 80 kV, 4 mA, 51 × 51 mm field of view, and 0.1/voxel (mm) size. The patients were then divided randomly into three equal groups (n = 20). After proper anesthesia and isolation, access cavities were completed with a round bur, followed by an Endo Z bur. Working length was determined using an apex locator (DENTA PORT ZX, Japan), and confirmed by periapical X-ray. Canal patency was established with a #15 K-type file (MANI, Vietnam) and RC prep glide path (Premier Dental, USA). Canals were prepared with the assigned instrumentation system according to the manufacturer's instructions and irrigated with 2 mm of a 2.5% sodium hypochlorite solution (NaOCl) (Clorox, Lebanon) followed by 3.0 mL of 17% ethylene-diamine-tetraacetic acid (EDTA) (NEXABIO, Korea) for 1 minute, and then 1.3% NaOCl as final irrigation. Tornado Finisher was used as directed by the manufacturer at 1 mm short of the working length in an up-and-down motion. In the other two groups, irrigation was performed with a 31G side-vented needle (Ultradent Products Inc.) placed passively into the canal, 1 mm short of the working length.Intracanal calcium hydroxide was added to the canals for one week. Every tooth in the three groups underwent the same obturation procedure (Lateral condensation technique) using gutta-percha (DiaDent, Korea) and sealer (META BIOMED, Korea). Finally, coronal preparation of all teeth was restored with composite filling (Ivoclar, Switzerland). Clinical evaluation was conducted at a one-year follow-up visit for each patient including spontaneous pain, sinus tract, swelling, mobility, periodontal probing depths greater than baseline, or sensitivity to percussion or palpation. A post-operative CBCT image was obtained and compared to the pre-operative one to assess the impact of canal preparation of each file on the periapical lesion based on Estrela et al.CBCT periapical index (CBCT PAI). The radiolucent area of the periapical lesion was measured in three dimensions on the CBCT scan. Bucco-palatal, mesiodistal, and diagonal measurements were obtained, and the greatest diameter was recorded for scoring the lesion extension . Measurements were conducted simultaneously and independently by two examiners and any discrepancies were discussed and remeasured for one measurement agreement. Cortical bone expansion (E) and cortical bone destruction (D) were included in the scoring system as appropriate. If either of these conditions was found in the CBCT analysis, the variables E and D were added to each score. Qualitative analysis of clinical evaluations was conducted for signs and symptoms. The pre- and post-operative Estrela et al. index scores were recorded. The Statistical Package for the Social Sciences software (SPSS 22, SPSS Inc, Chicago, IL) was used to perform the statistical analysis. The median was used to describe the qualitative data for all groups and normal distribution was tested using Shapiro-Wilk test. Since the data did not follow a normal distribution, the scores of the size of the apical lesion before and after one year were done for each group using the Wilcoxon signed ranks test while inter-group comparison was done using the Kruskal Wallis test followed by Mann-Whitney test for comparison of pairs. All statistical tests were performed at a p-value of 0.05.

Inclusion Criteria:

The patients should have lower molars with

• Two separate mesial canals.
• Distinct apical foramen.
• Mature periapical apices.
• No tooth cracks.
• No root resorption.
• Canal curvature for mesial canals ranged from 15° to 45°.

Exclusion Criteria:

• Patient who is younger than 16 or older than 65.
• Diabetic patient.
• Immune-compromising conditions.
• Patient has previous dental work on the working tooth.

IPD can't be shared due to ethical issues. IPD of this study is confidential.