Unused handpieces and handpieces which had been exposed to clinical dental procedures 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. This data suggests that a substance entrapped within ‘clinical’ handpieces (possibly the biofilm) may protect bacteria from ethylene oxide gas, preventing adequate sterilization.

One used dental handpiece from each hospital or department of stomatology in general hospital selected was detected for possible contamination of bacteria by aerobic bacterial count and CONCLUSIONS: dental handpieces without anti-suction should be replaced soon by those with it or comprehensive dental unit with anti-suction device should be used. Used dental handpieces must be sterilized effectively before next use. Awareness on prevention from cross-infection should be improved for dental-care professional staff and operation of sterilization should be standardized.

Then how to sterilize your low speed handpiece:

Wipe down the handpiece with a damp disposable cloth. If there is still some bioburden left on the handpiece, clean under running water using a brush. A mild detergent is acceptable. Be sure that all bioburden is removed before proceeding to the next step as it can act as a protective sheild for microorganisms in the autoclave sterilizer.