Tiny Bubbles Effectively Clean Instruments and Teeth

Richard Gawel


Sterilization is key to patient safety. Clinicians need to ensure their instruments are completely clean before using them again. Researchers at the University of Southampton have developed an ultrasound device that they say improves water’s ability to get tools clean—and teeth clean, too.

The StarStream supplies a gentle stream of water through a nozzle that generates ultrasound and tiny bubbles that automatically scrub surfaces. It dramatically improves the cleaning power of water while reducing the need for additives and heating, saving energy costs and pollution risks.

Using just cold water, the device removed biological contamination including brain tissue from surgical steel. It also removed soft tissue from bones, which is necessary before transplants to prevent rejection by the recipient’s immune system. And, it removed bacterial biofilms that typically cause infection and dental disease.

In one study, exposure to a water stream alone reduced mean biofilm biomass and thickness of Staphylococcus epidermidis by about 40% and 30% respectively, which the researchers did not consider statistically significant as a substantial amount of biofilm remained. The mean biomass of biofilms that were exposed to the activated stream, though, was reduced by about 97%.

“In the absence of sufficient cleaning of medical instruments, contamination and infection can result in serious consequences for the health sector and remains a significant challenge,” said Tim Leighton, a professor at the university’s Institute of Sound and Vibration Research.

“Our highly effective cleaning device, achieved with cold water and without the need for chemical additives or the high power consumption associated with conventional strategies, has the potential to meet this challenge and transform the sector,” Leighton said.

The StarStream outputs one to 2 liters of water a minute. It can work with tap water, so it can be attached to a simple faucet to provide a rinse or pre-clean instruments. Or, it can be added to an ultrasonic cleaning bath to thoroughly rinse away leftover film.

“Although ultrasonic cleaning baths are good, the item to be cleaned sits in a soup of contaminated liquid that is on the instrument as it is drawn out of the bath,” said Leighton.

Complicated tools on high-value instruments cannot be cleaned too vigorously, yet they have tissue on them and need thorough cleaning. With sterile services departments closed on weekends, tools used on Friday may wait 48 hours to be cleaned. Once these tools dry out, cleaning becomes much more difficult.

“Because StarStream can be fitted to the tap with little training, someone can give these tools a short inexpensive wash on Friday night so that when the main cleaning regime is implemented on Monday, most of the tissue has been removed,” said Leighton.

Later versions of the StarStream could be miniaturized to clean biofilms directly on teeth. Successful prototypes have been built, but none are in commercial production yet. During testing, the StarStream reduced the biomass of Streptococcus mutans biofilm on simulated teeth by 99.5%, while a water stream alone only reduced it by 20.7%.

S mutans is a key carcinogenic species and major risk factor for childhood caries and future caries development. Subsequently, the researchers believe the StarStream also has significant potential as an oral hygiene tool.

Published in Physical Chemistry Chemical Physics and in the Journal of Dental Research, the research was funded by the Royal Society Brian Mercer Award for Innovation. The University of Southampton has patented the StarStream, which now is in commercial production by Ultrawave Ltd.

“Commercialization is vital,” said Leighton. “If we cannot build a business that can sell thousands of these to health providers at a price they find attractive, this invention will stay in the laboratory and help no one.”

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