Modern dentistry can repair damaged or missing teeth, but its solutions remain imperfect. Fillings may wear out, implants lack nerves, and artificial crowns eventually need replacement, prompting scientists to pursue a more ambitious possibility: helping the human body grow living dental tissue and complete teeth.

Demand for something better is already clear. Some surveys suggest more than 70% of adults fear visiting the dentist, while biochemist Hannele Ruohola-Baker regularly receives emails from people asking to participate in experiments aimed at regrowing their teeth.

Ruohola-Baker, associate director of the University of Washington Institute for Stem Cell and Regenerative Medicine in the US, is among scientists using regenerative medicine to rethink dental care. "People are ready for something new in dentistry," she says.

The stakes extend beyond appearance. Pamela Yelick, a professor at the Tufts School of Dental Medicine in the US, says teeth influence eating, smiling, social confidence, emotional wellbeing, and wider health.

Bacteria from gum disease can increase the risk of heart disease and respiratory infections, and dental problems have also been linked to Alzheimer's disease. Tooth loss is associated with greater illness and earlier death, while limiting a person's ability to chew and eat properly.

Dentists currently treat cavities by removing damaged tissue and filling the space with materials such as resin composite. Yet fillings vary considerably in durability, lasting from about five to 20 years, and patients may require repeated procedures.

Anne George, a professor of oral biology at the University of Illinois, Chicago, studies proteins that help dentine grow, mineralise, and repair itself. She says existing procedures concentrate on "repairing damage, rather than restoring biological function," while regenerative dentistry "emphasises healing."

Teeth contain four main layers: enamel, dentine, cementum, and tooth pulp. Cavities begin when plaque bacteria consume sugars and produce acids that gradually dissolve enamel, exposing the softer dentine beneath it and increasing the risk of further decay.

George helped clone a gene involved in building dentine, providing insight into how teeth create and maintain the tissue. That knowledge could support treatments that stimulate teeth to repair cavity damage by producing new dentine, potentially removing the need to plug holes with conventional fillings.

Ruohola-Baker's team is pursuing a related approach focused on enamel. After examining donated wisdom teeth, researchers found that ameloblasts, the cells responsible for making enamel, die after a tooth erupts and therefore cannot simply be stimulated later.

The researchers instead used chemical signals to coax stem cells into becoming ameloblasts, while directing other stem cells to become dentine producing odontoblasts. When combined in a dish, the cells formed a tooth organoid capable of secreting enamel proteins independently.

Ruohola-Baker envisions using those proteins in fillings or painting them onto cracked teeth. Her longer term objective is to place engineered cells capable of building a tooth inside a patient's mouth and allow "nature take care of the rest."

Complete replacement teeth could also address limitations associated with implants. Implants do not contain nerves that provide sensation during chewing, making it possible to bite too forcefully and crack them, while bacteria can attach and cause problems affecting remaining healthy teeth.

Ana Angelova Volponi, director of regenerative dentistry at King's College London in the UK, is developing an organoid capable of becoming a replacement tooth. "Rather than just trying to patch what has been damaged, we could use a biological replacement," she says.

Volponi's team combined cells from adult human gum tissue with tooth forming cells from mice. The experiment produced a hybrid tooth structure made with human and mouse cells, including viable developing roots, and the researchers are now studying instructions and biomaterials that could help cells assemble into a functional tooth.

Yelick's team took another route by using human and pig tooth cells in adult Yucatan minipigs. Researchers grew the cells in a laboratory, placed them on a bioengineered scaffold, and saw structures resembling teeth develop after three months at a rate close to natural pig teeth.

Scientists remain years away from offering cavities that repair themselves or complete biological tooth replacements to patients. Ruohola-Baker says studies involving nonhuman primates must occur before human research can be considered, requiring additional research, time, funding, and better environments for tooth development.

Even so, regenerative dentistry may inform attempts to reproduce organs, bones, and other body structures. Because teeth are "highly sophisticated living organs," Yelick says efforts to recreate them reveal how hard and soft tissues function together.

Volponi remains confident that safe and sustainable regenerative treatments will eventually reach the public. "That's where I see the future," she says. "It's not very clear, but it’s hopeful."