An enlightened approach

REGENERATIVE medicine is a field with big ambitions. It hopes, one day, to repair or replace worn-out hearts, livers, kidneys and other vital organs. Many people, though, would settle for a humbler repair—of their teeth.

Dentistry has too much “drill and fill”, cutting away infected tissue and replacing it with alien, artificial materials. But if work by people such as David Mooney of Harvard University comes to fruition, the days of drill and fill may be numbered. For, as they report in Science Translational Medicine, Dr Mooney and his team have found a surprising way to get dentine, the tissue that underlies a tooth’s enamel coat, to repair itself. They do so by shining a laser beam at it.

Regenerative medicine boils down to the intelligent manipulation of stem cells. A stem cell is one that has the capacity to split asymmetrically so that one daughter remains a stem cell (and can thus go on to perform the same trick) while the other gives birth to a line which proliferates and differentiates into many other sorts of cell. The most famous, and controversial, stem cells are those in early embryos. These can turn into any sort of body cell. Mature tissues such as dentine contain stem cells of more limited capability, which keep up a supply of new specialised cells to replace old ones as they die.

Dr Mooney’s trick is to tickle dentine’s stem cells in a way that encourages them to proliferate and produce more dentine. And that is where the laser comes in. The light it shines creates chemically potent, oxygen-rich molecules such as hydrogen peroxide which go on to activate latent versions of molecules called transforming growth factor–beta 1 (TGF-beta 1). These, in turn, activate dentine’s stem cells and encourage the tissue’s growth.

Dr Mooney and his team have shown that this works in both tissue cultures and actual (rats’) teeth. Moreover, blocking the action of TGF-beta 1 with a drug, or by knocking out the gene that encodes the growth factor’s receptor, stops it happening, which suggests they have understood the mechanism correctly.

This is a preliminary result, and it does not address the question of whether enamel might similarly be repaired. But it is encouraging. Eventually, perhaps, dentists will approach cavities with lasers rather than drills—and the days of fillings will be over.