## 2 Materials and Methods  
### Sample Preparation  
The preparation of samples was performed according to [PERSON] et al. with slight modifications [20]. In our study, the criteria of the included teeth were teeth with closed apices and without any evidence of resorption, fractures, caries, previous endodontic treatment, or abnormal anatomy. Hence, any tooth that did not fulfill these criteria was excluded from the study. The teeth were stored in a 10% formalin solution for approximately two weeks before the beginning of the study for teeth preservation. Then, digital periapical radiographs were taken in facial and proximal views for each tooth to confirm the presence of a single straight canal. Each tooth was decoronated with a diamond fissure bur (final length: 14 mm \(\pm\) 1) below the level of the cemento-enamel junction. Canal patency was confirmed by fitting size 10 and 15 K-files (Dentsply Maillefer, Ballaigues, Switzerland) to the apical foramen, and all teeth were sterilized in an autoclave [20].  
The root canals were shaped with a sequence of ProTaper Gold NiTi Rotary Files (Dentsply Maillefer, Switzerland) using an X-Smart Endodontic Rotary Motor (Dentsply Sirona, NC, USA). The motor was set at 300 rpm and had a torque of 3/Nm (according to the manufacturer's instructions). Glyde gel (Dentsply Maillefer) was used during root canal preparation. A glide path was accomplished with the ProGlider file (Dentsply Maillefer; 0.16/0.02) along the working length. Root canals were instrumented tothe WL using the following file sequence: SX (0.19/0.04), S1 (0.18/0.02), S2 (0.20/0.04), F1 (0.20/0.07), and F2 (0.25/0.08), respectively, according to the manufacturer's recommendations. A patency K-file size of 10 was used between each rotary file. Sodium hypochlorite (NaOCL, 2.5%) was used as an irrigant with a syringe and a 25-gauge needle. To maintain the apical patency, a size 10 K-file was passed through the apex, and to remove the smear layer, the canal was rinsed with 3 mL of ethylenediaminettetraacetic acid (EDTA, 17%) (Produits Dentiares, SA, Veevey, Switzerland) for 1 min, followed by a final rinse with normal saline for 30 s. Finally, sterile paper points of size F2 (0.25 mm tip) were used to dry the canals before the obturation procedure [20; 21].  
All teeth were randomly divided into 3 groups, 2 experimental groups and 1 conventional group (\(n=10\)). Gutta-percha (size F2) master cones (TiaDent Inc., Houston, TX, USA) were disinfected by NaOCL (2.5%) for one minute followed by ethyl alcohol (70%). The obturation procedure was performed in aseptic conditions. Sealer placement was standardized using a 1 mL syringe to dispense 0.05 mL of sealer inside each canal without any additional sealer usage [22]. In group 1, MTA Fillapex bio-ceramic (MF) sealer was used for obturation of the root canal using a single gutta-percha cone. In group 2, CeraSeal bio-ceramic (CE) sealer was used for obturation of the root canal, similar to the previous group. Group 3 is the conventional (CO) group in which AH Plus (Dentsply Maillefer, Ballaigues, Switzerland) was used for obturation using a finger spreader by the lateral condensation technique. Excess gutta-percha was removed using a heated plugger. All specimens were stored in an incubator in 100% humidity at 37 \({}^{\circ}\)C for 7 days to allow the complete setting of the sealers.