Achievement of a deep and long-durated anesthesia is vital before most endodontic procedures; therefore, the investigators conducted this study to compare the local infiltration effect of epinephrine-containing lidocaine with/ without fentanyl on depth and duration of anesthesia in maxillary molars with painful irreversible pulpitis.

This study was planned with a randomized double-blind, parallel design clinical trial on 64 healthy patients after taking into account some inclusion and exclusion criteria. The control group were received the mixture of normal saline and 2% lidocaine with 1:200,000 epinephrine and the experimental group were received the mixture of fentanyl and 2% lidocaine with 1:200,000 epinephrine. The depth and duration of pulpal anesthesia were evaluated with an electric pulp testing in 5-minute intervals during a period of 60 minutes and the pain intensity recorded in five times, before injection, after injection, during access cavity preparation, pulpotomy and pulpectomy using visual analog scale(VAS). All data were analyzed and compared using chi-squared and Mann-Whitney tests.

Inclusion Criteria:

• Patients were aged between 18 and 65 years with no systemic diseases categorized in the Class I ASA;
• Individuals requiring urgent root canal treatment of maxillary first or second molars;
• Hot painful teeth with irreversible pulpitis (moderate to severe spontaneous pain), with a positive response to thermal vitality tests (a long painful response to a cold test) and no clinical or radiographic signs or symptoms of acute or chronic apical periodontitis; and
• No history of taking analgesics in the previous 12 h.

Exclusion Criteria:

• Systemic conditions;
• Allergic reactions to opioids, benzodiazepines, barbiturates;
• Pregnancy and lactation; Contraindication of the use of epinephrine (such as unstable angina);
• Nonvital pulp after access cavity preparation