Drills, X-rays, assorted sharp probes--these are the familiar, disquieting tools of dentists. Chris Longbottom, a dentist at the University of Dundee Dental School in Scotland, would like to add another item to that arsenal: electrodes that send electric currents through patients’ teeth and down their arms. To what end? Longbottom says the currents reveal incipient cavities that even X-rays might miss.
The process, Longbottom hastens to add, would be painless. Patients wouldn’t feel the tiny 10-millivolt current. The method takes advantage of the way cavities form. Bacteria in the mouth produce acids, which dissolve the minerals that make up teeth. This widens microscopic pores in teeth. Even before the pores widen into visible cavities, they decrease the electrical resistance of a tooth because the fluid in them is a better conductor than the solid tooth itself.
With special electrodes that fit over the places where teeth touch teeth, which are most vulnerable to decay, Longbottom and his colleagues have discovered that healthy teeth, teeth that are starting to decay, and teeth with full-blown cavities all have distinctive resistances. By measuring each tooth surface separately, they can pinpoint the site of decay. Current detection methods--X-rays or visual examination--spot only about 20 to 50 percent of the disease, and decay occurs inside a tooth before it becomes a cavity on the surface. Longbottom’s method catches the disease early enough to treat it fairly easily with fluoride or antibiotics, preventing painful and costly drilling later.
So far the Scottish dentists have tested the procedure only on removed teeth. Rather than attaching uncomfortable measuring devices to a patient’s cheek, in a full working version dentists would use small electrodes to send a current through the teeth and down one arm to a metal cylinder held in the patient’s hand. The cylinder would measure the out- coming current and feed it into a computer, which would tell the dentist if there’s decay.
Longbottom wants to start clinical trials in a year and hopes to have a completed product in four years. The first dental X-ray was taken in 1895, he says. Since then, there hasn’t been a new technique that’s improved on that and been clinically usable.