Experimental toothbrush with PVDF bristles generates charge while brushing; tested in 115 adults

Researchers have developed an experimental self-powered toothbrush whose bristles convert the friction of brushing into electrical charge, Live Science reports. The study was published Wednesday, Nov. 4, in Science Advances. The aim is to damage plaque-forming bacteria that survive mechanical cleaning. The brush was tested on isolated bacteria, on biofilms and in a trial with 115 adults. livescience.comLive Sciencelivescience.comOpen source ↗

How the bristles work

The bristles are made of polyvinylidene fluoride (PVDF), a plastic that generates electricity when bent, a property called piezoelectricity. Flexing during brushing produces a charge that triggers chemical reactions in saliva and water. These reactions release reactive oxygen species (ROS), highly reactive molecules that can damage bacterial cells. livescience.comLive Sciencelivescience.comOpen source ↗

The authors reported that the bristles carry a faint surface charge even when not in use, which helps keep bacteria from clinging to the brush head. When an antioxidant that neutralizes ROS was added, the antibacterial effect largely disappeared, so ROS are likely the key to the effect. The activity of genes for ATP-binding cassette (ABC) transporters fell in Streptococcus mutans and Porphyromonas gingivalis after exposure. Nicholas Jakubovics of Newcastle University, who was not involved in the study, was not convinced by this explanation. He noted that ABC transporters move many different substances and that the data did not clearly show how the gene changes affected the bacteria. livescience.comLive Sciencelivescience.comOpen source ↗

Laboratory and clinical results

In tests on isolated germs, the electrified bristles killed more than half of the S. mutans bacteria, which contribute to tooth decay. Nylon bristles killed 9%. P. gingivalis, linked to gum disease, fell by up to 78% with the new brush and by less than 8% with nylon. Human dental plaque grown on cow tooth enamel lost more than 99% of its biofilm, more than with a regular nylon brush. livescience.comLive Sciencelivescience.comOpen source ↗

In the trial, 115 adults with gum inflammation or tooth decay were randomly assigned to the new or a nylon brush, used twice a day for three months. The new-brush group had less plaque, less gum inflammation and less bleeding. Plaque samples showed lower levels of disease-associated bacteria and higher levels of beneficial ones. The authors suggest that disease-linked bacteria may have more fragile membranes, a theory that needs further study. livescience.comLive Sciencelivescience.comOpen source ↗

The PVDF bristles kept their structure and electrical properties over three months of simulated use. Mouse cells grown in the lab showed no damage from the brush material, and brushing did not roughen cow enamel. These tests cannot establish that long-term use is safe for humans, and further safety trials are needed. Jakubovics pointed out that in lab tests bacteria are exposed to the charge for hours, while in the mouth the bristle touches tissue only briefly. He regards the work as a proof of concept, and larger studies are needed. livescience.comLive Sciencelivescience.comOpen source ↗