Fluid/Solid Interactions in Teeth Cleaning

Innovative Personal Care products

Dr. Alex Ashcroft, Hard Surface Science Leader, Unilever Research Port Sunlight.

What’s the most effective way to clean your teeth? Use a lot or a little toothpaste? Slow or fast brushing? In circular motions or up and down?

The effectiveness of teeth cleaning relies on the interaction between the bristles of the toothbrush and the two components of the toothpaste – fine abrasive particles and a carrier fluid in which they are suspended.

The abrasion must be enough to provide maximum cleaning without causing damage to the surface of the tooth.

This project, which was sponsored by Unilever Research, set out to understand how particles act when loaded against a tooth and how they remove material from a solid layer. As well as having implications for toothbrush and toothpaste manufacturers it furthers medical research into preventing tooth decay and damage.

Optical apparatus was used to show how particles become trapped and move at the tips of toothbrush bristles. The motion of particles was especially marked at low brush loads and high sliding speeds – suggesting a little toothpaste may go a long way if you brush quickly enough.

"The Leonardo Tribology Centre helped design a toothbrush that took 20% of the European market on release"

Unilever had a turnover in excess of £44 billion in 2010, and is built on a commitment to investment in innovation. Many of the Home and Personal Care product ranges depend on the fundamental tribology taking place at surfaces and interfaces. Unilever has been working for several years with researchers in the Leonardo Centre to better understand these processes. Their work addresses areas of scientific and commercial importance for Unilever's Home and Personal Care brands, which, if successful, could deliver market disrupting and innovative products to consumers worldwide.