Tooth-mounted hearing aid for the masses

2010 preview: Tooth-mounted hearing aid for the masses Beethoven used a primitive version, but it’s something much more sophisticated that is set to restore hearing to people with a common form of deafness
by Linda Geddes

Beethoven is said to have overcome his deafness by attaching a rod to
his piano and clenching it between his teeth, enabling the musical
vibrations to travel through his jawbone to his inner ear. Next year,
a similar but less unwieldy approach might restore hearing to people
with a common form of deafness.

Single-sided deafness (SSD) affects around 9 million people in the US,
and makes it difficult for them to pinpoint the exact source of
sounds. This can make crossing roads extremely hazardous, and also
makes it hard to hear conversations in noisy rooms.

Sonitus Medical of San Mateo in California has created a small device
that wraps around the teeth. It picks up the sounds detected from a
tiny microphone in the deaf ear and transforms them into vibrations.
These then travel through the teeth and down the jawbone to the
cochlea in the working ear, where they are transmitted to the brain
providing stereo sound. The same process of “bone conduction” explains
how we hear our own voices, and why they sound different when they are
recorded and played back to us.

Some existing hearing aids also use bone conduction to transmit sounds
to the cochlea, but these either require a titanium post to be drilled
into the skull, or rely on cumbersome headsets. It also differs from
conventional hearing aids, which employ air conduction to simply turn
up the volume of sound travelling into the ear. The Cleveland Clinic
in Ohio voted Sonitus’s device its top medical innovation for 2010.

Sonitus is testing the device in people with SSD. One study suggests
the device is comfortable and doesn’t damage the teeth, and that it
improved speech intelligibility in noisy surroundings (Otology and
Neurotology, DOI: 10.1097/MAO.0b013e3181be6741). The firm may start
testing the device in people with other forms of deafness and at least
one functioning cochlea.

The company plans to submit its results to the US Food and Drug
Administration for approval in early 2010, and if all goes to plan,
the device should become available later in the year. It will lend an
ear to millions.