Effect of a Combination of Nitrous Oxide and Intraligamentary Injection on the Success of the Inferior Alveolar Nerve Block in Patients with Symptomatic Irreversible Pulpitis

Introduction The purpose of this prospective study was to determine the effect of a combination of nitrous oxide/oxygen and 1 set of supplemental intraligamentary/periodontal ligament (PDL) injections followed by a second set of PDL injections on anesthetic success in patients with symptomatic irreversible pulpitis (SIP). Methods Ninety-four patients with a mandibular posterior tooth diagnosed with SIP received nitrous oxide/oxygen and an inferior alveolar nerve block (IANB) with 2% lidocaine with 1:100,000 epinephrine. Patients rated the pain of PDL injections and endodontic access on a visual analog scale. If moderate to severe pain was felt during treatment, the operator administered 1 set of supplemental PDL injections with 4% articaine with 1:100,000 epinephrine. If moderate to severe pain was felt again during treatment, the operator administered a second set of supplemental PDL injections. Anesthetic success was defined as having no to mild pain during endodontic treatment. Results The success of the IANB with nitrous oxide was 44% (95% confidence interval [CI], 34%–54%). The overall anesthetic success rate (IANB with PDL injections) was increased from 69% (95% CI, 60%–78%) with 1 set of PDL injections to 80% (95% CI, 72%–88%) with a second set of PDL injections. Conclusions Although the second set of PDL injections increased anesthetic success, it was not sufficient to ensure complete pulpal anesthesia.