When a child’s baby teeth fall out, a permanent set of teeth has already grown under the gums, ready to grow in. But if we lose permanent teeth, there will be no new permanent teeth. Currently, the options for replacing these lost teeth are either dentures or titanium implants, but neither of these methods can provide the same function and feedback as real teeth.
Pamela Yelick (AG89), a professor at the Tufts University School of Dentistry, hopes to be able to grow new living teeth to replace the teeth we lose. In a paper published in late 2024, Yelick and her colleagues showed that they were able to use a combination of human and pig dental cells to grow human-like teeth in pigs. This work is an important step toward replacing dental implants with bioengineered living teeth.
Dental implants are usually based on titanium metal and fixed in the jawbone. Titanium metal bonds well to bone, but it lacks the soft tissue around natural tooth roots to buffer chewing forces and promote healthy bone turnover, and there are no nerves to provide sensory feedback.
If an implant is not perfectly aligned, or if chewing is too aggressive, the bone around the implant may begin to break down and be absorbed by the body. This creates an opportunity for bacteria to enter the implant, which can accelerate bone resorption and eventually cause the implant to fail.
“Even creating a root that can hold an artificial crown—with living pulp in the middle, held in place by the periodontal ligament, rather than screwed into the jawbone—could greatly improve a person’s oral health, and by extension, their whole body health,” said Jelick, who holds appointments in both the Graduate School of Biomedical Sciences and the College of Engineering.
Prompting the body to grow a new tooth is no easy task. Our teeth start out as a tooth bud—a small ball of cells inside the jawbone—that grows and differentiates into all the hard and soft tissues that make up the tooth and connect it to the jawbone. Researchers need to create their own bioengineered tooth buds that have the right cell types and instructions to grow into teeth on their own.
Tooth germs are made up of two types of cells: dental epithelial cells, which give rise to tooth enamel, and dental mesenchymal cells, which eventually form the rest of the tooth, including pulp, dentin, cementum, and periodontal ligament tissue.
Yelick and her team were able to collect dental mesenchymal cells from the pulp of extracted human wisdom teeth and other healthy teeth removed for orthodontic reasons, but dental epithelial cells are only present in the early stages of tooth development. Once teeth are formed, they cannot be harvested from humans. However, they can be harvested from unerupted teeth in pig jawbones.
Unlike humans, pigs grow multiple sets of adult teeth, so their adult jawbones contain extra tooth buds. The researchers obtained pig jawbones that would otherwise be discarded by slaughterhouses and extracted tooth buds from them.
They grew these tooth cells in the lab, along with cells from human teeth, and then added them to a bioengineered scaffold that helped provide the necessary cues to initiate tooth development. They then implanted these bioengineered tooth buds into the jawbones of adult pigs and monitored the animals for several months.
The researchers found that the bioengineered teeth developed at a similar rate to natural pig teeth, which is fairly close to the rate of human teeth. Because the experiment was only planned for three months, the teeth did not have a chance to erupt from the gums, but they went through the same developmental stages as natural teeth.
“We found that we can make these beautiful little teeth,” Jelick said. “They’re still in the jawbone—they haven’t erupted yet—but they look just like natural human teeth.”
Jelick and her colleagues hope to track the development of teeth over longer periods of time in future experiments. They are also studying the signaling molecules that guide cell behavior, looking for ways to initiate tooth growth from within the jawbone without having to extract and grow cells separately in the lab.
Their ultimate goal is to be able to prompt cells inside a person’s jawbone to grow brand new, fully human teeth—no pig cells required. There’s still a lot of work to be done before researchers can grow living replacement human teeth, but Jelick thinks it could be achievable within the next decade.
“Ideally, you keep your teeth for as long as possible. That’s the best-case scenario,” Jelick said. “But if something goes wrong, we want to have biological tooth replacements available.”
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