Symptomatic irreversible pulpitis is associated with a high incidence of inadequate pulpal anesthesia during endodontic treatment, particularly in mandibular molar teeth. Failure to achieve profound anesthesia may result in increased intraoperative pain and patient discomfort. Corticosteroids have been suggested as adjunctive agents to improve pain control and reduce inflammatory responses; however, the influence of different local administration techniques on anesthetic success and postoperative pain remains unclear.

The aim of this randomized controlled clinical trial is to compare the effects of submucosal and intraligamentary dexamethasone administration on anesthetic success and pain control in patients with symptomatic irreversible pulpitis. A total of 84 participants requiring root canal treatment of mandibular first or second molars diagnosed with symptomatic irreversible pulpitis will be randomly allocated to one of three groups: (1) inferior alveolar nerve block (IANB) followed by submucosal saline injection (control group), (2) IANB followed by submucosal dexamethasone injection, and (3) IANB followed by intraligamentary dexamethasone injection.

All participants will receive standardized endodontic treatment under local anesthesia. The primary outcome measure is anesthetic success during access cavity preparation and pulp extirpation. Secondary outcome measures include postoperative pain intensity at 6, 12, 24, 48, and 72 hours, and postoperative analgesic consumption. The results of this study may provide evidence regarding the effectiveness of different local dexamethasone administration techniques and contribute to improved pain management strategies in endodontic practice.

Symptomatic irreversible pulpitis is associated with a high incidence of failure of inferior alveolar nerve block anesthesia, particularly in mandibular molars, resulting in pain during endodontic treatment and the frequent need for supplemental anesthesia. Corticosteroids have been investigated as adjunctive agents because of their anti-inflammatory properties and their potential to improve anesthetic success and reduce postoperative pain. However, limited evidence is available regarding the influence of different local administration techniques on these outcomes.

This prospective, randomized, controlled, single-blind clinical trial aims to compare the effects of submucosal and intraligamentary administration of dexamethasone on anesthetic success and postoperative pain following inferior alveolar nerve block in patients with symptomatic irreversible pulpitis of mandibular first or second molars.

Eighty-four participants will be randomly allocated into three parallel groups (28 participants per group):

Group 1 (Control): Inferior alveolar nerve block followed by submucosal injection of normal saline (placebo).

Group 2: Inferior alveolar nerve block followed by submucosal injection of dexamethasone.

Group 3: Inferior alveolar nerve block followed by intraligamentary injection of dexamethasone.

The primary outcome is anesthetic success, assessed using the Heft-Parker Visual Analog Scale (HP-VAS) during access cavity preparation and pulp extirpation. Secondary outcomes include postoperative pain intensity assessed using the HP-VAS at 6, 12, 24, 48, and 72 hours after treatment, as well as the need for postoperative analgesic medication. The findings of this study may help identify the most effective local administration technique for dexamethasone to improve anesthetic success and postoperative pain management in patients with symptomatic irreversible pulpitis.

Inclusion Criteria:

• Patients aged 18 to 65 years.
• ASA I or ASA II systemic health status.
• Symptomatic irreversible pulpitis in a mandibular molar tooth.
• Positive response to pulp sensibility tests.
• Preoperative pain score greater than 54 mm on the Heft-Parker Visual Analog Scale (HP-VAS).
• Ability to understand the study procedures and provide written informed consent.

Exclusion Criteria:

• Pregnancy or lactation.
• Allergy or contraindication to articaine, dexamethasone, or study-related medications.
• Use of analgesics, anti-inflammatory drugs, or antibiotics within the previous 12 hours.
• Presence of periapical radiolucency or diagnosis of pulpal necrosis.
• Significant systemic disease (ASA III or higher).
• Inability to complete pain assessment forms or follow study procedures.

Individual participant data (IPD) will not be shared because there is no current data-sharing plan, and the study protocol and ethics approval do not include provisions for public sharing of individual participant-level data.