Bones mend, teeth do not, and that biological asymmetry has left millions living with gaps, dentures, or implants. A Japanese team is now testing a medicine that could restart natural tooth development, aiming to restore something modern dentistry has never truly replaced: living enamel, dentin, and root anchored to the jaw. The approach targets a brake on tooth formation called USAG-1, a protein that dampens growth signals known as bone morphogenetic proteins. In ferrets and mice, a monoclonal antibody that neutralizes USAG-1 reliably “unlocks” dormant dental programs, prompting new teeth to sprout. Because ferret dentition resembles ours, the results raised hopes that the same pathway can be nudged in people. Human testing began in September 2024 at Kyoto University Hospital. Over 11 months, researchers will intravenously administer the antibody to 30 men aged 30 to 64 who are each missing at least one tooth, monitoring safety and early signs of regrowth. If the data look good, the next cohort will be children ages 2 to 7 with congenital absence of four or more teeth, a rare condition that disrupts chewing, speech, and facial development. The near-term focus is congenital tooth deficiency, which affects about 1 percent of people, with severe oligodontia around 0.1 percent. But the same biology could eventually help those who lost teeth to cavities or trauma, offering a living alternative to prosthetics. Unlike a crown or implant, a regenerated tooth could remodel with the jaw and maintain sensation, circulation, and periodontal support. If all phases succeed, the team hopes to make the therapy available around 2030. That timeline remains contingent on rigorous proof, yet the concept marks a milestone in organ regeneration, where the goal is not a replacement part but restored biology. Source: 10.1126/sciadv.abf1798 - @science