Anesthetic efficacy of unilateral and bilateral inferior alveolar nerve blocks to determine cross innervation in anterior teeth

Objective. The purpose of this prospective randomized study was to measure the degree of anesthesia obtained with unilateral and bilateral inferior al veolar nerve blocks to determine whether cross innervation occurs in anteri or teeth. Study design. Through use of a repeated-measures design, 38 subjects random ly received unilateral or bilateral inferior alveolar nerve blocks at two s eparate appointments. Each inferior alveolar nerve block used 3.6 mL of 2% lidocaine with 1:100,000 epinephrine. Mandibular anterior teeth were blindl y pulp-tested at 4-minute cycles for 60 minutes' postinjection. No response from the subject to the maximum output (80 reading) of the pulp tester was used as the criterion for pulpal anesthesia. Anesthesia was considered suc cessful when 2 consecutive 80 readings were obtained. Results. One hundred percent of the subjects had lip numbness with each of the inferior alveolar nerve block techniques. Anesthetic success rates of t he unilateral inferior alveolar nerve block were 39% for the central inciso r, 50% for the lateral incisor, and 68% for the canine. For the bilateral i nferior alveolar nerve blocks, success rates were 66% for the central incis or, 74% for the lateral incisor, and 76% for the canine. The bilateral infe rior alveolar nerve block success rates were significantly (P < .05) higher for the central and lateral incisors when compared with the success rates of the unilateral inferior alveolar nerve block. Conclusions. Cross innervation does seem to occur in mandibular central and lateral incisors. However, the success rates in these teeth with bilateral inferior alveolar nerve blocks were below 75%. The failure of the inferior alveolar nerve blocks to anesthetize the anterior teeth was the overriding reason for failure. Clinically, bilateral inferior alveolar nerve blocks t o provide profound pulpal anesthesia in mandibular anterior teeth are not r ecommended on the basis of the results of this study.