A placebo-controlled, double-blind, crossover trial on analgesic effect of nitrous oxide-oxygen inhalation

The sedative effect of nitrous oxide-oxygen (N2 O/O2 ) inhalation is relatively well established. Less in known about its analgesic effect.

To determine the analgesic effect of N2 O/O2 inhalation on pulp sensitivity and jaw muscle pressure pain threshold in children.

A placebo-controlled, double-blind, crossover trial with random allocation to two sequences: atmospheric air at the first session and N2 O/O2 at the second; or N2 O/O2 at the first session and atmospheric air at the second. Measurements included reaction time, pulp pain sensitivity, jaw muscle pressure pain thresholds and a VAS score of overall discomfort from the pain tests.

Fifty-six children (12-15 years) completed the study. N2 O/O2 inhalation increased reaction time (P < 0.001). Pulp pain sensitivity was reduced during N2 O/O2 inhalation (P < 0.001), but no effect was found after adjustment for the increased reaction time. Pressure pain threshold on the jaw muscle was also reduced during N2 O/O2 inhalation (P < 0.001), also after adjustment for reaction time (P < 0.005). An effect was still found 10 min after the mask had been removed (P = 0.03). No effect on VAS scores of discomfort from the tests could be found.

No analgesic effect of N2 O/O2 inhalation on pulp pain sensitivity was found, whereas an increased pressure pain threshold of jaw muscles was found.