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

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.

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.

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.

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.

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.