The effects of various dental procedures and patient behaviors upon nitrous oxide scavenger effectiveness.

This prospective study of 36 children, ages 44-93 months, receiving nitrous oxide-oxygen under standardized conditions during routine dental procedures was conducted to determine what influence eight selected dental procedures and three patient behaviors had on ambient nitrous oxide (N2O) levels in the dentist's breathing zone. Half the children received nitrous oxide-oxygen via a scavenging nasal mask. An infrared spectrophotometer analyzed the ambient N2O level continuously throughout the procedure and the time-weighted average (TWA) for consecutive 15-sec intervals was recorded by a microprocessor. A video camera was used to synchronize the coded dental procedures and patient behaviors to the TWA ambient N2O levels recorded. The results demonstrated that scavenging significantly reduced the dentist's exposure to ambient N2O (P less than 0.05, nonscavenged mean = 284.7 ppm; scavenged mean = 36.6 ppm), but the mean TWA N2O concentration remained significantly higher, P less than 0.05, than the 25-ppm level recommended by the National Institute for Occupational Safety and Health (NIOSH). Supplemental oral evacuation was the only dental procedure capable of reducing ambient N2O to below NIOSH's recommendation when scavenging was employed. The administration of local anesthesia consistently created a significant increase in ambient N2O levels. Patient behaviors of talking, crying, and movement also resulted in significant increases from baseline ambient N2O levels.