Injection pain: comparison of three mandibular block techniques and modulation by nitrous oxide:oxygen.

BACKGROUND: The authors conducted this study to compare the pain on injection of the three mandibular block techniques and to determine the effect that the delivery of nitrous oxide:oxygen, or N2O:O2, had on this pain.

METHODS: Based on sample size calculation, the authors randomly assigned 60 subjects to receive either local anesthetic alone or local anesthetic with N2O:O2 titrated to effect. Each subject received two mandibular block injections bilaterally from three possible pairings: Gow-Gates/standard block, standard block/Vazirani-Akinosi or Gow-Gates/ Vazirani-Akinosi. Subjects scored their pain using a 100-millimeter visual analog scale immediately after each injection. The authors analyzed data using analysis of variance, Student t tests and multiple regression analyses.

RESULTS: There were no significant differences in pain on injection among the three injection techniques. The subjects in the group that received N2O:O2 and the local anesthetic demonstrated a statistically significant reduction in pain on injection compared with subjects in the group that received the local anesthetic only (P < .05). When N2O:O2 was used, there was a statistically significant decrease in pain with the first injection (P < .0005), an effect not seen with the second injection.

CONCLUSIONS: There was no significant difference in pain among the three mandibular block techniques. N2O:O2 can reduce pain on the first injection given, but this effect is not seen subsequently.

CLINICAL IMPLICATIONS: The decision to select one of the three mandibular block techniques should be based on factors other than pain on injection. N2O:O2 reduces pain on the first injection only.