Your teeth are one of the only parts of your body that can't naturally repair themselves – so when a kid injures a permanent tooth at a young age, they're stuck with that for life. But a new clinical trial has shown promising results in using dental stem cells derived from a patient's baby teeth to bring a "dead" tooth back to life.

The study builds on previous work that investigated human deciduous pulp stem cells (hDPSC), which may be able to replenish pulp – the soft, innermost tissue of a tooth. To find out, the trial involved 40 children who had all injured one of their permanent incisors. Most of those patients were treated using hDPSCs, while a control group of 10 underwent apexification, the current standard procedure for this kind of injury.

Patients in the test group had hDPSCs extracted from the pulp of one of their healthy baby teeth, which were then grown in a lab before being implanted into the injured tooth. The researchers followed up with the patients after treatment, and found that one year later those who had received the stem cell treatment had regained some sensation in the injured tooth, while the control group had not.

"This treatment gives patients sensation back in their teeth," says Songtao Shi, co-lead author of the study. "If you give them a warm or cold stimulation, they can feel it; they have living teeth again. So far we have follow-up data for two, two and a half, even three years, and have shown it's a safe and effective therapy."

Further follow-ups over the years revealed that the test group seemed to have healthier root development, increased blood flow and thicker dentin, the tough middle layer of a tooth. Interestingly, in one case a patient reinjured the treated tooth and had to have it extracted, giving the researchers the chance to directly examine it. Sure enough, the stem cells had regenerated cells that produce dentin, connective tissue and blood vessels inside the tooth pulp.

As promising as the results are so far, the process might not seem like much help for adults who lost all their baby teeth many moons ago. The researchers are planning to test using hDPSCs donated from other people, but that brings with it the chance of the recipient's body rejecting the implant.

Luckily, there are other similar treatments in the works. A few years ago researchers in London managed to grow "bioteeth" using gum tissue and embryonic cells from mice. Other teams found that low-power lasers or a type of Alzheimer's drug can both stimulate stem cells to kick into gear and naturally repair damage to dentin and pulp.

Altogether, it brings hope that the days of fillings and root canals might be numbered.

The new research was published in the journal Science Translational Medicine.

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