All procedures were performed by a endodontist (XX) only in patients who met the inclusion criteria. All patients were informed about the risks of the study and alternative treatment options before participating. Anaesthesia was achieved with 4% articaine hydrochloride containing 1:100,000 adrenalin. None of the patients required additional anaesthesia. After rubber dam isolation, previous caries and restorations were removed with high and low speed sterile burs under water cooling. The previous root canal obturation of all teeth included in the study was removed with a similar treatment protocol. All files were used with a torque-controlled endodontic motor based on the appropriate torque and rpm values specified by the manufacturer. After determining the canal length with an electronic apex locator the apical patency was checked with a #10 K hand file. During the procedure, the canal was continuously irrigated with 5.25% sodium hypochlorite. In all irrigation procedures, a 27-gauge side-vented irrigation needle was used, which was set to be 2 mm shorter than the working length. No solvent was used during the NSER protocol. The literature has found that there is no definite consensus on the final apical diameter of the root canal when applying NSER. However, it has been reported that in primary endodontic treatment, the preparation should be completed with a larger file than the file used for apical region preparation. In this study, the final preparation was completed by using a case-specific file that was chosen to be larger than the apically compressed file while making the final preparation. The root canal was prepared with rotary files. For the final irrigation procedure is 2 mL of 5.25% NAOCl, distilled water, 17% ethylene diamine tetraacetic acid , distilled water, 2% chlorhexidine solutions were used respectively. The root canal were dried with paper points . Then, all teeth were randomly assigned one of the three study groups by using online software (http://www.random.org). (n:21).

Cold Lateral Compaction (CLC-Control Group): After the root canal preparation was completed, the working length was checked with the master cone and periapical radiography. The master cone was then covered with root canal sealer and placed in the root canal. Then, a gap was created for the .02 angled lateral cones using #30, 25 and 20 finger spreader. The obturation process continued until the spreader went 2 mm beyond the level of the canal orifice. Next, a hot excavator removed the coronal gutta-percha 1 mm below the canal orifice.

Continuous Wave Compaction (CWC): After the root canal preparation was completed, the working length was checked with the master cone and periapical radiography. Root canal sealer was applied to the root canal walls using a master cone. The plugger connected to the down-pack unit was adjusted to be 4 mm shorter than the working length. The master cone was cut 1 mm shorter than the working length with a heated plugger and applied to the root canal. Then, the heated plugger was advanced in the apical direction and the apical region was obturated. Obturation was completed in 2 stages with gutta-percha in the cartridge connected to the remaining root canal cavity back-fill unit and heated to 200 °C. Heated gutta-percha was vertically condensed with plugger to 1 in the first stage and 2 in the second. The root canal obturation was completed by removing the gutta-percha 1 mm below the canal orifice.

Thermoplasticized Gutta-Cor (TGC): After the root canal preparation was completed, the working length was controlled with the master cone and periapical radiography. Root canal sealer was applied to the root canal walls using a master cone. Root canal obturation was completed with gutta-percha heated according to the manufacturer's instructions using. The heated gutta-percha was slowly inserted into the canal up to the working length. After cutting the handle of the obturators at the level of the canal orifice with a hot excavator, it was condensed into the canal using a gutta-percha plugger. The coronal gutta-percha were removed 1 mm below the canal orifice using a hot excavator.

In the same visit, all teeth were permanently restored using direct composite resin .