Effectiveness of ethylene oxide for sterilization of dental handpieces

Ethylene oxide gas has been utilized as an alternative method for sterilization of dental handpieces, as it is less corrosive than steam. However, its effectiveness for sterilization of the internal components of dental handpieces has not been established. The objective of this study was to compare the effectiveness of ethylene oxide and steam for sterilization of dental handpieces. Unused handpieces and handpieces which had been exposed to clinical dental procedures ('clinical') were contaminated with Streptococcus mutans, exposed to steam or ethylene oxide, and flushed with sterile saline. Washings were plated on mitis-salivarius agar, and colonies identified and counted. No viable colonies could be established from washings from 'clinical' or 'unused' handpieces exposed to steam. However, viable colonies could be established from 'clinical' handpieces exposed to ethylene oxide. This data suggests that a substance entrapped within 'clinical' handpieces (possibly the biofilm) may protect bacteria from ethylene oxide gas, preventing adequate sterilization.