Armed with that information, Dr Ruohola-Baker and her colleagues next checked to see whether the stem cells could be persuaded to transform into ameloblasts.
The team devised a cocktail of drugs designed to activate the genes that they knew were expressed in functioning ameloblasts.
That did the trick, with the engineered ameloblasts turning out the same proteins as the natural sort.
A different cocktail pushed the stem cells to become odontoblasts instead.
Culturing the cells together produced what researchers call an organoid—a glob of tissue in a petri dish which mimics a biological organ.
The organoids happily churned out the chemical components of enamel.
Having both cell types seemed to be crucial: when odontoblasts were present alongside ameloblasts, genes coding for enamel proteins were more strongly expressed than with ameloblasts alone.
For now, the work is more a proof of concept than a prototype of an imminent medical treatment.
The next step, says Dr Ruohola-Baker, is to try to boost enamel production even further, with a view to eventually beginning clinical trials.
The hope is that, one day, medical versions of the team’s organoids could be used as biological implants, to regenerate a patient’s decayed teeth.
Stem-cell-based therapies are not the only ones heading to clinical trials.
Another class of treatments is known as biomimetic repair.
This involves rebuilding the tooth crown using synthetic proteins, which are similar, but not quite identical, to human enamel.
Unlike stem-cell treatments, the proteins could be included in toothpaste, mouthwash and even cough drops.
But synthetic formulations can be less durable than human enamel.
It will take time for either technology to arrive in the clinic.
One question is just how durable the enamel made by stem-cell-derived ameloblasts proves to be.
Another is how best to deliver the stem cells to a patient’s mouth.
But these findings are promising.
As any dentist will tell you, prevention is better than cure.
But a better cure would be welcome nonetheless.