Visiting the dentist isn't just a pain in the jaw-it's also a pain in the pocketbook. Clinical physicists at the Glasgow Dental Hospital and School in Scotland are helping to reduce both types of pain with a carbon dioxide laser that drills tooth cavities without burning the surrounding gums and teeth. The CO2 laser's infrared wavelength is ideal for the job because it is readily absorbed by the tooth's dentin and enamel. To avoid cracking of dental tissue around the drilling site, the system uses short pulses of light instead of a continuous beam. Because CO2 lasers are a well-established technology, the makers of the new drill, John Whitters and Ronald Strang, claim it will be significantly cheaper than today's dental lasers-solid-state systems based on erbium embedded in a crystal of yttrium aluminum garnet, or YAG. The scientists have teamed up with an undisclosed laser manufacturer and plan clinical trials later this year.