The significance of needle deflection in success of the inferior alveolar nerve block in patients with irreversible pulpitis

The purpose of this prospective, randomized, blinded study was to compare the anesthetic efficacy of the conventional inferior alveolar nerve block, administered with the needle bevel oriented away from the mandibular ramus, to the bidirectional-needle-rotation technique, administered using the computer-assisted Wand 11 anesthesia system, in patients diagnosed with irreversible pulpitis. Sixty-four emergency patients diagnosed with irreversible pulpitis of a mandibular posterior tooth randomly received, in a blinded manner, 2.8 ml of 2% lidocaine with 1:100,000 epinephrine using either a conventional inferior alveolar nerve block or a bidirectional-needle-rotational technique using the Wand 11 injection system. The conventional inferior alveolar nerve block was administered with the needle bevel oriented away from the mandibular ramus so the needle would deflect inward toward the mandibular foramen. The bidirectional -needle-rotation technique was administered by rotating the Wand handpiece assembly in a clockwise-counterclockwise movement (like an endodontic hand file) to minimize needle deflection. Endodontic access was begun 17 min after solution deposition, and all patients were required to have profound lip numbness. Success was defined as none or mild pain (VAS recordings) on endodontic access or initial instrumentation. The results of this study showed no significant differences (p > 0.05) between the success rates of the two techniques. The conventional inferior alveolar nerve block, with the needle bevel oriented away from the mandibular ramus, had a 50% success rate. The bidirectional-needle-rotation technique with the Wand 11 had a 56% success rate. Neither technique resulted in an acceptable rate of anesthetic success in patients with irreversible pulpitis.