Addition of 2 mg dexamethasone to improve the anesthetic efficacy of 2% lidocaine with 1:80,000 epinephrine administered for inferior alveolar nerve block to patients with symptomatic irreversible pulpitis in the mandibular molars: a randomized double-blind clinical trial

INTRODUCTION: This clinical trial aimed to evaluate the anesthetic effect of the addition of 2 mg (4 mg/ml) of dexamethasone to 2% lidocaine (plain or with 1:80,000 epinephrine). The solutions were injected for a primary inferior alveolar nerve block (IANB) to provide mandibular anesthesia for the endodontic treatment of mandibular molars with symptomatic irreversible pulpitis. METHODS: In a double-blinded setup, 124 patients randomly received either of the following injections: 2% lidocaine with 1:80,000 epinephrine, 2% lidocaine with 1:80,000 epinephrine mixed with 2 mg dexamethasone, or plain 2% lidocaine mixed with 2 mg dexamethasone, which were injected as a primary IANB. Ten minutes after injection, patients with profound lip numbness underwent electric and thermal pulp sensibility tests. Patients who responded positively to the tests were categorized as “failed” anesthesia and received supplemental anesthesia. The remaining patients underwent endodontic treatment using a rubber dam. Anesthetic success was defined as “no pain or faint/weak/mild pain” during endodontic access preparation and instrumentation (HP visual analog scale score < 55 mm). The effect of the anesthetic solutions on the maximum change in heart rate was also evaluated. The Pearson chi-square test at 5% and 1% significance was used to analyze anesthetic success rates. RESULTS: The 2% lidocaine with 1:80,000 epinephrine, 2% lidocaine with 1:80,000 epinephrine mixed with 2 mg dexamethasone, and plain 2% lidocaine mixed with 2 mg dexamethasone groups had anesthetic success rates of 34%, 59%, and 29%, respectively. The addition of dexamethasone resulted in significantly better results (P < 0.001, χ(2) = 9.07, df = 2). CONCLUSIONS: The addition of dexamethasone to 2% lidocaine with epinephrine, administered as an IANB, can improve the anesthetic success rates during the endodontic management of symptomatic mandibular molars with irreversible pulpitis.