Tooth Tingles

by Paul McGoldrick

It’s a great feeling, isn’t it, when you leave the dentist’s office after a routine cleaning? Your credit card has been weighted down by the worse part of a couple of hundred dollars but your tongue responds to your teeth with that twice a year feeling of clean. Most of us do our best between those visits to maintain those clean teeth and to minimize the length of the next dental visit. And, quite childishly, we revel in the praise of the hygienist that we have been good boys and girls between appointments.

Some people go to even further trouble than that hand-held toothbrush (mine are always “free” from the dentist’s office) and invest in a rotary brush buzzing around at some frequency somewhere in the audio passband. Whichever way we go we all feel civilized to avoid the Russian approach of using salt by buying a toothpaste that suits our taste and marketing brain cells. Some will go for a whitener; some for a fluoride; some for baking soda; some of us will combine the lot. For my part as an electronics engineer fluoride is scary, with hydrogen fluoride (HF) in its aqueous form as hydrofluoric acid reminding me only of childhood etching of printed-circuit boards in the family bathtub. (No, you don’t want to know what it did to the bath enamel…)

Now along comes a Japanese dentist, Dr Kunio Komiyama, who is Emeritus Professor of Dentistry at the University of Saskatchewan, with a toothbrush described as revolutionary that will eliminate the use of toothpaste.

As one might expect the operational details of the toothbrush are, at best, sketchy: “The Soladey-J3X has a solar panel at its base that requires minimal amounts of light to transmit electrons to the head of the toothbrush through a titanium dioxide semiconductor embedded in the body.”

The operational description goes on to suggest that the electrons react with acid in the mouth that breaks down plaque and kills bacteria.

Wow! Nylon conducting electrons…

The information that we do know about the construction of the brush is that there is a solar panel at the bottom connected to a titanium dioxide (TiO₂) filament running up through the top part of the center of the brush to the nylon head. The toothbrush handle is described in wonderful Japanese English as a “metallic body with a special processing on plating that raises the electrical current rate.”

Wow! Is that a cute way of saying low resistance?

The titanium dioxide is described as a semiconductor which, indeed, it could be. There are dye-sensitized solar cells (DSSCs) using wide gap semiconductive nanocrystalline titanium dioxide thin films and, perhaps, the whole of the inside stem is in fact part of the solar cell. One of the advantages of such solar cells is that they have relatively high conversion efficiencies for simple construction techniques. Most of us associate naturally-produced titanium dioxide with whitening processes – such as the white lines on Wimbledon’s tennis courts, or the paint on the outside of Saturn rockets – and it has also been used, with hydrogen peroxide, in teeth whitening products. But it does not seem to be related directly to teeth in this application.

This toothbrush is not really completely new in that the Japanese company, Shiken, produced a solar-powered toothbrush about fifteen years ago and what we are seeing now is a further development of that device. There is, reportedly, a study of one hundred and twenty teenagers going on using the new brush to compare it with conventional cleaning with brush and paste. There have been patents issued in nine countries for the toothbrush and production versions of the latest iteration are expected to be available early in 2011 with pricing around €40 (about US$50).

The quasi-technical explanation of this toothbrush operation is either deliberately vague or just a total sham. My bet would be on some kind of static electric effect in the nylon bristles from the voltage produced from the solar cell. Electrons directly zapping plaque and bacteria is just too silly a claim to take seriously. If it tingles, like a battery across your tongue, that will not remind me of my dental hygienist’s work at all. I’ll probably stick with ultrasonics…