Peking University team develops self-charging toothbrush that cut plaque in trial

Centre · 2Researchers in China have developed a toothbrush whose bristles generate their own weak electric current as they bend during brushing, and a clinical trial found it reduced plaque, gum inflammation and bleeding more than a conventional nylon brush. 1 2 Centre · 2The bristles are made from a piezoelectric plastic, which the South China Morning Post identifies as polyvinylidene fluoride (PVDF). The current drives the production of reactive oxygen species, which damage bacteria, while the bristles also remove plaque physically. 2 1 Centre · 2The work comes from Peking University and was published online in the journal Science Advances, according to the SCMP. The SCMP names Zhang Xuehui, director of the Dental Materials Laboratory at the university's School and Hospital of Stomatology, as corresponding author. New Scientist names Yanhui Lu of Peking University as the researcher leading the team. 2 1

Centre · 1In laboratory tests, New Scientist reports, the thicker piezoelectric bristles killed about 53 per cent of Streptococcus mutans, which causes cavities, and 78 per cent of Porphyromonas gingivalis, which contributes to gum disease. Nylon bristles killed 9 and 8 per cent respectively. 1 Centre · 2Plaque grown from human mouths on pieces of cow enamel was brushed for 3 minutes, and the new brushes removed more than 99 per cent of it, against about 80 per cent for nylon. The SCMP also cites a cleaning efficiency of over 99 per cent and good biocompatibility in laboratory and animal experiments. 1 2 Centre · 2In the human trial, volunteers were randomly assigned to the piezoelectric or a nylon brush for three months. New Scientist counts 109 adults using their brush twice daily and reports reductions of roughly 40 per cent in plaque, gum inflammation and bleeding, against around 15 per cent for conventional brushes. The SCMP counts 115 volunteers, with tooth and gum diseases such as periodontitis or dental caries, and says all received identical instructions on toothpaste and brushing. 1 2

Centre · 2The SCMP says no volunteers reported pain, numbness or electric shocks. New Scientist adds that the bristles met Chinese national standards for softness and strength, stayed soft and kept their electrical properties after three months of use, and that sequencing of plaque from the piezoelectric group showed fewer harmful bacteria and more potentially beneficial ones. 2 1 Centre · 2Outside researchers and the authors both call for more evidence. Nicholas Jakubovics of Newcastle University, who was not involved, called the concept "great" and "really innovative", but said larger studies must show whether the brush prevents cavities and tooth loss. Zhang said further comparisons with existing technology are needed to establish the new technique's advantages. 1 2 Centre · 1Earlier approaches include brushes with antibacterial silver or zinc nanoparticles in the bristles, whose long-term effectiveness is uncertain, and ionic brushes that use electric currents to loosen plaque but depend on batteries. 1