A 39-year-old California woman testing a revolutionary new hearing aid that works through a tooth reports that it made it possible to hear clearly everywhere except at a Metallica concert.

“I had problems holding a conversation while they were playing (I had an ear plug in my good ear), but my husband said that even for him it was next to impossible,” said Gloria on a discussion forum for people with deafness.

The woman, who didn’t disclose her last name, described the end of her 60-day clinical trial of the Sonitus SoundBite on Jan. 23 as “kinda sad.”

Sonitus Medical will apply soon for U.S. government approval for the device, which conducts sound through a back tooth rather than the conventional method of turning up the sound on air travelling into the ear. The company hopes to have the device on the market by mid-2010.

The hearing aid didn’t interfere with speaking or eating and “continues to give hope to a huge group of us with single-side deafness who are waiting for something non-invasive,” Gloria said.

SoundBite starts with a custom-built device fitted to a molar and a wireless microphone within the ear canal. A digital audio device worn as a thin cord behind the ear picks up the sound from the microphone and transmits it to the tooth device, which produces sound vibrations that reach the cochleae through the bone. While some hearing aids use bone conduction to send sounds to the cochleae, they also require a titanium post to be drilled into the skull.

New Scientist magazine described it as a 21st century version of Beethoven’s method for circumventing his deafness: a rod attached to his piano then clenched in his teeth to pick up musical vibrations.