Tooth decay may finally have met its match. A small study of a new mouthwash found that it kills virtually all of the bacteria that cause tooth decay, but leaves other, beneficial oral bacteria alone. Its inventor likens it to a smart bomb. And he thinks it could wipe out tooth decay in our lifetime.

Nearly all tooth decay is caused by a single species of bacteria, Streptococcus mutans. Conventional mouthwashes are only effective against it for a few hours and indiscriminately kill other beneficial mouth bacteria. And while toothbrushing certainly helps prevent cavities, also known as dental caries, sometimes it's not enough. Tooth decay is a problem faced by over half the people in the nation.

Enter C16G2, the active ingredient in the mouthwash and the product of over a decade's worth of research.

Nearly all tooth decay is caused by a single species of bacteria. Conventional mouthwashes are only effective against it for a few hours and indiscriminately kill other beneficial mouth bacteria.

Wenyuan Shi, a UCLA microbiologist, has been working for years to design small compounds that kill only specific types of bacteria. They work by linking together a small compound that kills bacteria with a second small compound that targets the package to a single species of bacteria. Shi calls these compounds STAMPs, small targeted anti-microbial peptides.

In the case of C16G2, the STAMP is made of a portion of the broad-spectrum antibiotic Novispirin G10 linked to a portion of a Pheromone naturally produced by Streptococcus mutans called competence stimulating peptide. The pheromone guides the molecule to S. mutans; the antibiotic kills it. Quickly.

It's not quite as simple as it sounds. A STAMP made by combining the full length antibiotic and pheromone wasn't effective. Getting one that worked required quite a bit of molecular tinkering and ended up shortening the two compounds before linking them together.

Shi's lab has also come up with STAMPs that are effective against species of Pseudomonas, bacteria that cause many hospital-acquired infections.

One problem with antibiotic use is that they're indiscriminate, killing both helpful and harmful bacteria. Another is that they eventually breed resistance into the bacteria exposed to them. STAMPs should help limit this because only the target bacteria end up getting exposed to antibiotic. The technology is too new for anyone to be certain about its long-term effects.

People have been living with S. mutans practically ever since there have been people. Like our gut bacteria, it's been a constant companion, though not a friendly one. If Dr. Shi's mouthwash can truly eliminate it or even curb it, millions will be smiling.

Larger trials are scheduled to begin in March.

An article on the effectiveness of the mouthwash appears in the November, 2011 issue of Caries Research.