Nanosilver Toothbrush

We have an array of bristle toothbrushes in our collection that are all slight variations on the same two hundred and fifty year-old technology: a forest of soft, fine and stiff filaments that are punched at regular intervals into a hard and rigid handle. These brushes are all used, more or less effectively, to remove impacted food and bacterial plaque from the teeth and gums without injuring them.

We have been fashioning tools for keeping our mouths clean for a very long time, with the earliest ones dating back to 3500BC. These first artefacts for oral hygiene were not toothbrushes as we currently know them, but chewing twigs, toothpicks or rags soaked in salt or soot. The first recognisable bristle brushes were developed in China between 1000 and 1400CE and were made from hog and horse hair embedded in bone.

In Europe we lagged behind in the oral hygiene department, with the first toothbrushes appearing from the 18th century, along with a rise in consumption of refined sugar and a Victorian obsession with personal hygiene. Pig bristles were used for cheaper brushes and badger hair for the high-end. However, animal hair isn’t the ideal material for the job: being porous, it absorbs water and retains bacteria. Following the invention of nylon in the 1930s, animal hair was replaced with more hygienic synthetic bristles, and celluloid handles replaced bone.

This particular toothbrush has polymer bristles that are coated or blended with silver nanoparticles to prevent the built up of bacteria on the bristles. Silver, gold, zinc and other metal nanoparticles have been increasingly embedded in consumer products over the last fifteen years or so, in an attempt to find biocides that do not encourage antibiotic resistance in bacteria. These nano-enabled consumer products have been shown to effectively kill microbes, but their effectiveness varies depending on the chemical composition, size, charge and shape of the nanoparticles used, and the species of bacteria they encounter. We are also still uncertain about the long term health effects of using these metallic nanoparticles so widely, and it is unclear whether bacteria could develop resistance to metal nanoparticles over the long term too.