Hugh Pickens writes "The first electric dental drill was patented in 1875; modern drills grind the diseased portions of teeth away at up to 500,000 rpm. But dentists have been seeking less invasive ways of wiping out stubborn, tooth-decaying bacteria. Now Live Science reports that bacteria-killing jets of plasma could soon replace the drills used to treat cavities in our teeth. Researchers recently demonstrated that a small, blowtorch-like device emitting a relatively cool beam of purple plasma could eliminate oral bacteria in cavities, leaving more tooth structure intact than a drill does. To test how well 'cold' plasma jets (about 100F or 38C) sterilize tooth material, researchers took slices of dentin from extracted human molars, doused them with bacteria, and torched them with the plasma jet. An inspection via a scanning electron microscope of the damage done to the germs shows bacterial remnants had holes in their cell walls. When the plasma jet fires, it charges oxygen in the surrounding air, creating highly reactive molecules that can break down the bacteria's defenses. Researchers believe the technique could be available to general dentistry in three to five years."