Background: This study compared the safety and efficacy of nitrous oxide (N2O)/midazolam and N2O/promethazine for dental treatment of uncooperative children. Materials and Methods: In this randomized, cross‑ over, clinical trial investigation Eighteen healthy uncooperative children with a pair of similar teeth requiring the same treatment were included. Combination of N2O/midazolam was given in one visit, where N2O/promethazine was administrated in the other appointment for each patient in a cross‑ over manner. Oxygen saturation and heart rate as well as behavior parameters according to Houpt behavior scales were recorded. Postoperatively, patients’ anxiety and parents’ satisfaction were assessed by visual analog score and a questionnaire, respectively. Data were analyzed using Wilcoxon’ s signed rank test and Paired t‑ tests with a P value set at 0. 05. Results: Physiologic parameters were within normal limit in both groups. Children in midazolam group were significantly deeper sedated compared to other groups. In the first phase, children sedated with midazolam behaved superiorly in comparison to promethazine, while there was no difference at the final phase of the treatment between the two groups. Conclusion: Both of the drug combinations resulted in acceptable, efficient, and safe sedation outcomes.

Background: Nitrous oxide (N2O) is the oldest anesthetic in routine clinical use and its occupational exposure is under regulation by many countries. As studies are lacking to demonstrate the status of nitrous oxide levels in operating and recovery rooms of Iranian hospitals, we aimed to study its level in teaching hospitals of Tehran University of Medical Sciences.Methods: During a 6-month period, we have measured the shift-long time weighted average concentration of N2O in 43 operating and 12 recovery rooms of teaching hospitals of Tehran University of Medical Sciences.Results: The results show that the level of nitrous oxide in all hospitals is higher than the limits set by different countries and anesthetists are at higher risk of exposure. In addition, it was shown that installation of air ventilation could reduce not only the overall exposure level, but also the level of exposure of anesthetists in comparison with other personnel.Conclusion: The high nitrous oxide level in Iranian hospitals necessitates improvement of waste gas evacuation systems and regular monitoring to bring the concentration of this gas into the safe level.