9%) children. Table 2 shows descriptive statistics of the response at the three tests at baseline, and 15 min after the mask had been placed and the inhalation started. No statistically significant difference in reaction time (P = 0.17) was found at baseline between the two sessions (23). N2O/O2 inhalation significantly increased the reaction time with 183 ms (P < 0.001), whereas no effect was found 10 and 30 min after the mask had been

removed. (Table 3) Baseline values for tooth-pulp pain sensitivity were not statistically significantly different between the two sessions (Table 4). At the test 15 min after the mask had been placed and inhalation started, the average value was 92.7 μA during inhalation of N2O/O2 and 54.0 μA during inhalation of atmospheric. This represents a statistically highly significant reduction in tooth-pulp pain sensitivity of 38.7 μA (P < 0.001) (Table 4). PFT�� After adjustment for increase in reaction time,

however, this effect could not be demonstrated. No effect was found 10 and 30 min after the mask was removed. Baseline pressure pain thresholds of the masseter muscle did also not show any difference between the two sessions. At the test 15 min after the mask had been placed and inhalation started, the average value was 312.5 kPa during inhalation of N2O/O2ir and 231.7 kPa during inhalation of atmospheric air. This represents a statistically check details highly significant increase of 80.8 kPa (P < 0.001)

(Table 4). This effect was reduced to 47.8 kPa, but still statistically significant (P < 0.005) after adjustment for increase in reaction time. In contrast to the findings for tooth-pulp pain sensitivity, an effect on pressure-induced muscle pain could still be seen 10 min after the mask had been removed (P = 0.03), even after adjustment for increase in reaction time (P = 0.04). No effect was found 30 min after the mask find more had been removed. The VAS score for overall discomfort from the two experimental pain tests was almost identical (N2O/O2 inhalation sessions: average: 1.23; SD: 0.19; atmospheric air sessions: average: 1.18, S.D.: 0.18), and the difference is not statistically significant. This finding was not influenced by adjustment for increase in reaction time. The present study has not been able to show any analgesic effect on tooth-pulp sensitivity, after the increase in reaction time caused by the drug has been taken into account. In contrast, an analgesic effect on pressure-induced muscle pain was found, also after adjustment for the increases in reaction time. We opted to assess both tooth-pulp pain sensitivity and jaw muscle pain sensitivity because different oro-facial tissues may have different sensitivity to painful stimuli and different responses to analgesic interventions. Furthermore, both odontogenic types of pain and musculoskeletal pains are frequently encountered in children.