Losing a tooth has always been treated as permanent. Once adult teeth are gone, the options are limited to implants, bridges, or dentures. That assumption may soon be challenged.
Japanese researchers have begun human trials of an experimental drug designed to regrow teeth—something previously thought impossible in adults. After years of animal research, the study marks the first real test of whether tooth regeneration can work safely in people.
Why Teeth Don’t Regrow Like Bones
Bones are living tissue built to remodel. They have a blood supply throughout, a large pool of active cells that both break down and rebuild bone, and a repair process that is triggered when bone senses damage and mechanical stress.
Teeth are built differently. The outer layer, enamel, has no living cells and no blood supply, so once it is chipped or worn away the body cannot rebuild it. Under enamel is dentin, which is living tissue, but its repair capacity is limited. The cells that make dentin can lay down a small amount of new protective dentin when irritated by early decay, grinding, or minor injury, but this response is slow and modest. It is not designed to rebuild large areas of lost structure.
Tooth development also depends on specialized tissue structures that exist during early formation and then disappear after the tooth erupts. Once those developmental programs shut down, the body does not normally keep an active system on standby to produce a whole new tooth crown and root on demand. On top of that, teeth have tight physical constraints. They sit in a fixed socket, connect to the jaw through a ligament that absorbs biting forces, and contain nerves and vessels concentrated in the pulp. When damage reaches deep layers, the pulp can become inflamed or infected, and the usual result is treatment or extraction rather than regrowth.
The Protein That Blocks Tooth Growth
USAG 1 is short for uterine sensitization–associated gene 1, a protein better known in biology as SOSTDC1. It acts as a signal blocker during development, meaning it can dampen the growth messages that tell certain tissues when to form and how much to form.
Tooth formation depends on a tightly timed conversation between tissues in the developing jaw. A big part of that conversation runs through bone morphogenetic proteins, often shortened to BMPs. BMP signals help guide early tooth patterning and the steps that eventually shape a tooth. USAG 1 can interfere with that signaling, which is why researchers see it as a key bottleneck. The drug approach described in your sources is built around a simple idea: if USAG 1 is reducing tooth forming signals, neutralizing it may let those signals run stronger in the places and windows where tooth development can still be triggered.
In practice, the treatment being tested is an antibody therapy designed to bind to USAG 1 and limit its ability to block BMP related signaling. Antibodies are used in medicine to target specific proteins with high precision. Here the target is not a virus or a tumor marker, but a naturally occurring protein that appears to restrain tooth growth. The scientific bet is that turning down that restraint could unlock tooth regeneration without needing implants or graft materials.
As Katsu Takahashi, head of dentistry at the medical research institute at Kitano Hospital in Osaka, explained in an interview with The Mainichi, “We want to do something to help those who are suffering from tooth loss or absence. While there has been no treatment to date providing a permanent cure, we feel that people’s expectations for tooth growth are high.”
What Animal Studies Have Shown So Far
Animal studies are used to confirm two things before human testing begins: that a treatment can trigger the intended biological effect and that it does not cause obvious harm. In tooth regeneration research, this means checking whether new tooth structures actually form in the jaw and whether those structures resemble real teeth rather than incomplete or abnormal growth.
Researchers also watch closely for unintended effects, especially because the therapy targets developmental signaling pathways. Animals are monitored for changes in feeding, oral inflammation, pain behavior, and abnormal tissue growth elsewhere in the body. These checks help rule out broad disruptions beyond the teeth.
Before moving to human trials, the antibody was tested in mice and ferrets. Ferrets are particularly relevant because they share a similar pattern of having two sets of teeth. In these studies, treated animals developed new teeth, and no serious safety concerns were reported.
Commenting on the earlier results, Takahashi said in a Kyoto University press statement, “We knew that suppressing USAG-1 benefits tooth growth. What we did not know was whether it would be enough.” Animal results cannot predict how well the approach will work in adults, but they provided enough evidence to justify carefully controlled human trials.
Inside the First Human Trial
Human trials began in September 2024 and are designed as an early stage safety and feasibility study rather than a test of clinical usefulness. The goal at this point is not to restore full chewing function or replace existing dental treatments, but to determine whether the antibody can be given safely to adults and whether it triggers any sign of tooth formation at all.
The study is being conducted at Kyoto University and Kitano Hospital and enrolls adult men who are missing at least one molar. Limiting the group to a narrow population helps researchers reduce biological variability and better interpret early signals. This kind of cautious enrollment is standard for first in human studies that target developmental pathways.
Participants receive the drug intravenously so researchers can tightly control dosing and monitor how the antibody moves through the body. Over the course of the study, investigators track local changes in the jaw as well as general health markers to watch for unintended effects. Imaging and clinical exams are used to assess whether any new tooth structures begin to form and whether those changes remain stable over time.
Because this phase focuses on safety and biological response, it is not designed to measure long term durability, bite strength, or cosmetic outcomes. Those questions would only be addressed in later trials if this initial study shows that the approach is tolerable and biologically active in humans.
Why Children Are the Next Focus
If the adult trial confirms safety, the research will expand to younger patients.
The next planned group includes children ages 2 to 7 with congenital tooth deficiencies, specifically those missing four or more teeth. These conditions currently have limited long-term treatment options.
Researchers see pediatric cases as an important step because children’s jawbones are still developing, which may support more predictable tooth formation.
While the initial focus is congenital conditions, Takahashi has stated that the long-term goal is broader access for anyone who has lost teeth.
When Could This Be Available?
Despite the attention this research is receiving, it remains early stage work. The current human study is only designed to answer basic questions about safety and whether the drug produces any measurable biological response. Even positive results at this stage would not be enough to support clinical use.
Before the treatment could be offered outside of research settings, it would need to move through additional trial phases involving larger and more diverse groups of participants. Those studies would need to confirm that new tooth formation is consistent, that the teeth develop in a usable and stable way, and that no delayed safety issues appear over time. Researchers would also need to determine appropriate dosing, timing, and which patients are most likely to benefit.
Regulatory review would follow successful trials. That process involves close examination of safety data, manufacturing standards, and long term monitoring plans. This step alone can take years, even for therapies that show strong early results.
Researchers involved in the project have suggested that the earliest possible timeline for broader availability would be around 2030. That estimate assumes later trials confirm reliable tooth formation, acceptable safety over extended follow up, and results that remain consistent across different age groups. Until those requirements are met, implants, bridges, and dentures will continue to be the standard options for managing missing teeth.
What This Means for Patients Right Now
For now, this research should be viewed as promising but experimental. It does not mean people should delay necessary dental treatment or expect tooth regrowth to replace implants anytime soon. However, it does represent a shift in how scientists think about dental care, moving away from replacement and toward regeneration.
If successful, a tooth regrowing drug could reduce the need for invasive dental procedures, lower long term costs, and preserve natural chewing and sensory function. The idea that adults might one day regrow lost teeth was once considered unrealistic. Human trials make it a scientific question rather than a hypothetical one. The next few years will determine whether this approach delivers on its promise or remains an impressive but limited experiment.
