The aim of the study, treatment procedures, possible side effects and treatment alternatives will be explained to the patients. Patients will be asked to follow the general instructions and sign a printed informed consent. Patients will be asked to fill the outcomes data charts honestly and accurately.
* Eligible patients will be randomly divided into two equal groups according to randomization mechanism: Group 1 (Comfort-In Jet Anesthesia) and Group 2 (Local Infiltration Anesthesia)
* Pre-operative measures (for all groups):
* Medical and dental history will be obtained from all participants, clinical and radiographic evaluation for each tooth included in this study will be recorded.
* Clinical diagnosis of symptomatic irreversible pulpitis will be confirmed based on both subjective and objective findings.
* The operator will explicitly explain the trial steps to the patients, and an informed consent will be signed by patients who accept enrolment.
* Pain scale chart will be explained to each participant in order to be used after administration of local anaesthesia.
* Intervention group (G1): Teeth will be anaesthetized using the Comfort-In Jet device by administering 1 ml of 4% Articaine buccally and 0.5 ml palatally.
* Control group (G2): Teeth will be anaesthetized using conventional infiltration anaesthesia by administering 1 ml of 4% Articaine buccally and 0.5 ml palatally.
* Each patient will record the level of discomfort during administration of anaesthesia in the pain scale chart (NRS).
* Profound pulpal anaesthesia will be checked using an electric pulp tester reading every one minute after anesthetic administration up to ten minutes.
* Teeth that fail to reach profound pulpal anaesthesia will receive a rescue dose of the same anaesthetic solution (4% Articaine) using the conventional injection technique, if needed, intra-ligamentary injection will be used followed by intra-pulpal anaesthesia in case of persistent pain.
* After confirming profound pulpal anaesthesia single visit root canal treatment will be performed.
* Access cavity preparation will be done using round burs and tapered diamond stones and patients will be asked to report any pain and/or discomfort during this step. The pain intensity will be recorded on the NRS.
* Teeth will be isolated with rubber dam and working length will be obtained by an apex locator and confirmed radiographically to be 0.5 to 1 mm from the radiographic apex.
* All canals will be prepared with crown down techniques using EdgeEndo rotary files depending on the initial size of the canals.
* Irrigation will be done using 2 ml of 2.5% NaOCl between each two successive files, then, all canals will have a final flush with 5 ml of 17% EDTA for 1 minute followed by 5 ml of distilled water, 5ml of 2.5% NaOCl and finally 5 ml of distilled water in order to remove any residual chemicals from canals.
* Pain incidence and intensity during mechanical preparation will also be reported by the patients and recorded on the NRS.
* After complete preparation canals will be dried and obturated in the same visit and teeth will be temporized.
* Patients will receive postoperative instructions, and will be allowed to call the operator in case of moderate or severe postoperative pain and if needed, an emergency visit will be scheduled.
