The bacteria that cause tooth decay could be killed by microscopic “bombs” detonated with an ultrasonic toothbrush.
Ultrasound can cause some liquids, such as perfluorohexane (PFH), to rapidly expand and turn into a gas. Some researchers have explored the use of tiny, degradable capsules containing these liquids to deliver drugs into the body or to kill cancerous tumors.
Now, Xian-Zheng Zhang at Wuhan University in China and colleagues have developed capsules containing HFPs designed to destroy biofilms (aggregations of microbes on a surface) that are a common cause of dental cavities and infections.
The micrometer-sized capsules, which Zhang and his team called microbombs, contain molecules of calcium peroxide, iron, and tannic acid. When struck with ultrasound, the PFH causes the micropumps to rupture, setting off a chain reaction that converts calcium peroxide to hydrogen peroxide, which destroys biofilms.
Ultrasonic toothbrushes, which produce high-frequency sounds above the human hearing threshold to dislodge bacteria-filled plaque from teeth, can be used to detonate microbombs.
To test its effectiveness, Zhang and his team treated biofilms derived from human saliva with micropumps and ultrasound and found no detectable bacteria survived.
They then attempted to treat plaque-bearing rats with a micropump-laden toothpaste and an ultrasonic toothbrush every day for three weeks. Two other groups of rats received either a common oral antiseptic or no treatment. The group treated with the micropump toothpaste had the least enamel damage and cavities.
This use of microcapsules is novel, he says Stephen Evans at the University of Leeds, UK, but it’s not clear how better it might be at destroying biofilms than a regular toothbrush. It would be interesting to see how effective it is in disrupting biofilms in harder-to-reach places, like inside the body, he says.
