Purpose: The aim of this prospective, double-blind, randomized controlled trial is to compare the effect of oral premedication of dexamethasone, ketorolac, meloxicam, ibuprofen or placebo on the success of inferior alveolar nerve blocks (IANB) of mandibular posterior teeth in patients experiencing symptomatic irreversible pulpitis. Methods: The trial will include five study groups, each consists of 50 patients who exhibits symptomatic irreversible pulpitis of a mandibular first or second molar. The patients will receive identically appearing capsules containing either dexamethasone 0.5 mg, ketorolac 10 mg, meloxicam 7.5 mg, ibuprofen 600 mg, or placebo by mouth 60 minutes before the administration of an IANB. Endodontic access will begin 15 minutes after completion of the IANB. The IANB success is defined as no or mild pain (Heft Parker visual analog scale recordings) on pulpal access or instrumentation.

This study is designed as a randomized, double-blind, placebo-controlled trial. This trial follows the most recent update of the Declaration of Helsinki criteria (October 2013). The Vision Colleges Research Ethics Committee approved the clinical trial protocol and informed consent. The Consolidated Standards of Reporting Trials guidelines will be used to report the present superiority study. Participants under the age of 18, those with a history of major medical issues, those who had used central nervous system depressants or any analgesic drug in the preceding 6 h, those who were pregnant, and those who were unable to give informed consent will be excluded from the study. All the patients will sign a consent form that had been approved.

The inclusion criteria will be active pain in the first or second mandibular molar, a prolonged response to cold testing, no periapical radiolucency on periapical radiographs, and a vital coronal pulp on access opening. The Modified Dental Anxiety Scale will be used to assess the patients' anxiety levels. The pain of the patients will be categorized into four categories using the Heft-Parker visual analogue scale (HP VAS):

0 mm: no pain 0-54 mm: faint, weak, or mild 55-114 mm: moderate pain >114 mm: strong, intense, and maximum possible Permuted block randomization will be used to ensure the homogeneity of the five groups. The patients will be randomly given dexamethasone 0.5 mg, ketorolac 10 mg, meloxicam 7.5 mg, ibuprofen 600 mg, or placebo by mouth 60 mins before administering IANB. To blind the experiment, each of the 50 patients in each group will be randomly allocated a code consists of 2 letters and one number. Only the random codes will identify the medications; thus, the patient and clinicians are uninformed of which medication will be given to them. At 60 mins after taking the medication or placebo, the operator will use a cotton tip applicator to put anaesthetic gel at the IANB injection site for 60 s.

The participants will then give regular IANB injections and 0.9 mL long buccal injections containing 2% lidocaine and 1:100,000 epinephrine. Each patient will be asked for lip numbness every 5 mins for 15 mins after the IANB. The block will be considered missed if substantial lip numbness was not reported by 15 mins, and the participant will be excluded from the trial. After the lip numbness is determined, the tooth will be isolated and a second cold test will be performed to verify the presence or absence of any painful reaction.

After that, the endodontic access will be conducted. During the endodontic process, patients will be asked to rate any pain they experienced. If the patient is in pain, the treatment will be stopped, and the patient will use the HP VAS to rate his/her discomfort. The success of the IANB is identified by the capability to access and clean and shape the root canal space without pain (VAS score of 0) or mild pain (VAS rating ≤54 mm). The rubber dam will be removed if the patient had moderate or severe pain (VAS rating ≥ 55 mm). Then, a buccal infiltration of a cartridge containing 4% articaine with 1:100,000 epinephrine will be given buccally to the tooth that required emergency treatment. After 5 mins, the rubber dam will be replaced, and endodontic access will be resumed. The capability to access and instrument the tooth without pain (VAS score of 0) or with mild pain (VAS rating ≤54 mm) is considered a success of the buccal infiltration. Intraosseous anesthesia will be given to the patients who still had moderate to severe pain. The intraosseous injection will be given. If that didn't work, an intrapulpal injection will be given, followed by endodontic debridement. The extent of access preparation and/or instrumentation will be recorded as within dentine, within pulp space, and instrumentation of canals.

The VAS satisfaction form will be used to record the post-treatment satisfaction of the patient. On the VAS (0-100 mm), the patient will be asked to draw a vertical line to represent their experience with the entire treatment. The VAS is classified into four categories; 0: not satisfied, >0 mm and ≤33 mm: somewhat satisfied, >33 mm but <66 mm: moderately satisfied and ≥66 mm: completely satisfied.

Inclusion Criteria:

• active pain in a mandibular molar first or/and the second molar
• prolonged response to cold testing
• absence of any periapical radiolucency on periapical radiographs
• vital coronal pulp on access opening
• able to give informed consent

Exclusion Criteria:

• less than 18 years old
• history of serious medical problems
• used central nervous system depressants or any analgesic medication within the previous 6 hours
• pregnancy
• inability to give informed consent

To blind the experiment, each of the 50 patients in each group will be randomly allocated a code consists of 2 letters and one number. Only the random numbers identify the medications; thus, the patient and doctor are uninformed of which medication will be given to them.