Computerised toothbrush makes oral hygiene a game

17:45 04 April 2008
NewScientist.com news service
Colin Barras

Here's a novel way to encourage young children to brush up on their oral hygiene – turn a toothbrush into a simple version of a Nintendo Wii remote and turn a chore into a fun computer game.

Parents or professionals trying to teach young children to brush their teeth are faced with two problems. Many youngsters are unwilling to brush their teeth in the first place. Then, even if they can be persuaded, they often lack the skill to brush them effectively – for example, the average five-year old brushes only a quarter of their teeth.

Hao-hua Chu and his team at the National Taiwan University have come up with a novel solution using a "learning through play" approach.

To the end of a normal toothbrush they added a simple box-shaped extension with a unique pattern of three LEDs on each face. These LEDs that can be tracked using computer vision technology.
Webcam tracking

A webcam mounted on the wall above the bathroom sink can then track brush movements in three dimensions and feed this information into a computer. The computer distinguishes the orientation of the brush, and can also track its x-axis "roll" and z-axis "yaw".

This information can used to determine the position of the toothbrush head and to work out precisely which teeth the bristles are in contact with at any given moment.

"We initially tried using motion sensors – 3D accelerometers – similar to the ones in the Wii remote," says Chu. "But we were only able to accurately detect four rough teeth areas: upper-lower, and left-right."

The LEDs and a wall-mounted camera may seem low-tech, but Chu's team found the approach could accurately distinguish 24 different areas in the mouth. Similarly, they found there was little to gain by adding a second webcam to more precisely track the movement of the toothbrush. "A dual camera system is more difficult to set up," adds Chu.

The next step was to design a simple computer game using input from the new "Playful Toothbrush" – turning a tedious task into a fun one. The game uses sound and vision to encourage children to scrub colourful dirt from a set of virtual teeth shown on a computer screen. As the child cleans their own teeth, they see an instant impact on the virtual teeth.
Twice as effective

Chu's team tested the Playful Toothbrush on a class of 13 kindergarten children. The researchers used plaque-disclosing dye to assess the effectiveness of the children's brushing technique before and after five days using the Playful Toothbrush. They found that the children were twice as effective at cleaning their teeth following the trial.

"I was confident it would work, based on 25 years' clinical experience with children," says Jin-Ling Lo, an occupational therapist on Chu's team. "But the results are beyond my expectations."

BJ Fogg, a pioneer of "persuasive technologies" at Stanford University, California, is not surprised by the results. "In general, this approach is effective," he says. Similar games have helped motivate subjects to exercise more, and to engage in boring tasks such as labelling digital photographs.

"The hard part is the detail of the game," he says. "Just because people make a game out of a task doesn't mean it will work."

Chu's team are already considering how modified versions of the game could appeal to older children. "For older children or adults, the design considerations may be slightly different," he says. "Users could download their preferred games according to their age and gender."

The results were presented at the 26th Computer and Human Interaction conference in Florence, Italy, in April.