## 2 Materials and Methods  
The Institutional Review Board approved the study HSC-DB-18-0844. Urgent Care Clinic patients requesting the extraction of symptomatic mandibular molar teeth, rather than accepting endodontic treatment, were asked to participate in the study and informed consent was obtained by the principal investigator (DEJ). The teeth were selected based on the pulpal and periapical diagnosis and anatomical similarities as well as the acceptability of the teeth for the multisonic technology procedure. Previously treated, cracked, or fractured teeth were not selected. A total of 24 teeth with the diagnosis of symptomatic irreversible pulpitis (SIP) (N = 12 teeth) and pulp necrosis with symptomatic apical periodontitis (SAP) (N = 12 teeth) were selected. Immediately after extraction, each tooth was placed in an individual test tube containing 20 mL of phosphate buffered solution (PBS), except for control group teeth that were placed immediately in a 10% buffered formalin solution. The average length of the roots was 11 mm \(\pm\) 1.7 mm and the curvature degree was 20.5\({}^{\circ}\)\(\pm\) 10.5\({}^{\circ}\) for all specimens [36]. Digital periapical radiographs (buccal and mesial views) were taken to evaluate the teeth for similarities in terms of root length, number of root canals, and root curvature, to ensure that the teeth had similar root canal anatomy. All similar teeth were evaluated under the dental microscope (Global Inc., Saint Louis, MO, USA) to make sure that none had any root fractures. All clinical procedures were completed immediately after the teeth were extracted. After the evaluation of the teeth, the crown of each tooth was disinfected by rubbing the crown with wet 2 \(\times\) 2 gauze impregnated with 6% NaOCl. The access cavities were made with a high-speed handpiece with a sterile # 2 round carbide bur (Brasseler, Savannah, GA, USA) under constant water spray. The root canal orifices were located with a DG-16 endodontic explorer (HY-Friedy, Chicago, IL, USA) and a # 10 K file (Kerr, Brea, CA, USA) was used to explore the root canals and gain patency. Working length was established per manufacturer instructions (1.5 mm short of the apical foramen). The roots were completely covered with a thick layer of hot glue in the furcation area and around the roots to create a closed system which mimics the root when it is enclosed by the bone socket (Kerr, Brea, CA, USA). After initial instrumentation with # 10 and # 15 K hand files (Kerr, Brea, CA, USA), all the canals were enlarged using Vortex Blue (Dentsply, Tulsa, OK, USA) # 15/04 and # 20/04 as recommended by the manufacturer. Then, 1 mL of 3% NaOCl was delivered inside the root canal using a 5 mL syringe with a 30G irrigation needle (Dentsply, Tulsa, OK, USA) after each file. After preparing the root canals, an occlusal platform was created using Sound Seal (Sonendo Inc., Laguna Hills, CA, USA) per the manufacturer's instructions. The occlusal platform was reaccessed using a # 557 carbide bur (Brasseler, Savannah, GA, USA) to the cavosurface margin of the original endodontic access. Then, a depth gauge was used to measure the depth of the pulp chamber. The corresponding sealing cap to the depth gauge was then selected and attached to the procedure instrument (PI) per manufacturer instructions. The PI was placed on the platform (Figure 1), ensuring that the sealing cap was fully seated to create a sealed environment. Then, the foot pedal was depressed to start the procedure. A sealed platform on the tooth is essential to prevent entry of air into the tooth which could impede the propagation of the energy and fresh fluids into the canal system. The initial cycle is a leakage test with distilled water for 1 min. The purpose is to verify a completely sealed environment between the tooth and the procedure instrument (PI) as well as to ensure the appropriate flow rate and optimize the procedure fluids.