Scientists say they have found a way to use stem cells extracted from baby teeth to regrow dental tissue in permanent teeth.

In a study published in the journal Science Translational Medicine, researchers from the University of Pennsylvania and the Fourth Military Medicine University in Xi'an, China looked at how to treat children who suffered an injury during childhood.

Damage to a baby tooth when children trip or fall can affect blood supply and root development, leading to a “dead” tooth, which can appear gray in color. Treatment for this has typically involved apexification, which encourages the development of the root, but lost tissue does not get replaced.

In this study, the team found that using dental stem cells, they could better help children recover from these injuries. In a Phase I trial in China involving 40 children, who had damaged an adult incisor but still had baby teeth, an experimental treatment was used.

Of those children 30 were given the new treatment, called human deciduous pulp stem cells (hDPSC), which uses stem cells extracted from one of their baby teeth that the researchers then allow to reproduce in the lab before implanting them into the injured tooth.

The other 10, the control group, were treated with apexification.

The results showed that those given the hDPSC treatment had better root development than the control group. What’s more, after a year, only those with the hDPSC treatment had regained some sensation in the tissue of their injured teeth.

"This treatment gives patients sensation back in their teeth,” Songtao Shi of the University of Pennsylvania, a co-author on the study, said in a statement. “If you give them a warm or cold stimulation, they can feel it; they have living teeth again.”

The team said that even three years later, the new treatment looked to be both safe and effective. And in one case, when a child reinjured their tooth, the stem cells were successful again in treating the tissue, restoring the connective tissue and blood vessels.

The team noted, though, that as the treatment uses a patient's own stem cells, it only worked for patients who still had their own baby teeth – so it’s not possible in adults who have lost all of theirs. However, they are looking for approval in the US to treat adult teeth with stem cells donated from another person.