A Harvard-led team just successfully used low-powered lasers to activate stem cells and stimulate the growth of teeth in rats and human dental tissue in a lab.

The first step for researchers was to drill holes in two rat molars, exposing the interior of the tooth underneath.

They exposed dentin, which is the harder-than-bone but softer-than-enamel tissue that teeth are mostly made of. Then, they lit up the dentin using a low-powered laser, trying to get the stem cells there to kick into action and start producing more dentin to replace the damaged area.

When tested with human dental stem cells, the effects were similar. The lasers activated the stem cells, which can become many different types of cells, and specifically caused them to start forming dentin.

Top image an exposed rat molar that received the treatment causing it to start to regrow.
Bottom image showing structure of tooth cells as the regenerative process begins.

Quoted text via Business Insider.