Progress has been made, but growing human teeth remains largely out of reach. By Andy Kollmorgen
For most people, two sets of teeth just aren’t enough. After all, nearly every Australian has undergone some form of restorative dentistry such as a crown or a bridge or at least had a few teeth filled.
It doesn’t help that most Australians put off going to the dentist, making periodontitis and tooth loss that much likelier. And, of course, the use of dental implants increases year on year and has become a ripe field of opportunity for many practitioners.
But what if you could grow a new tooth once the first two have given way to decay, not unlike an amphibian miraculously regrowing a limb?
Some see this heady prospect as not only viable but inevitable, at least within the context of animal studies in the laboratory. So far, nobody has said scaling up to humans would be cheap or practical.
In 2009, professors Mark Bartold and Stan Gronthos of Adelaide’s Institute of Medical and Veterinary Science embarked on a regenerative dentistry project using pigs’ and sheeps’ teeth, which are prone to some of the same sorts of dental woes as human teeth.
The research involved taking stem cells from dental pulp located between the dentine and cementum areas of the animal’s teeth, and the researchers were optimistic that growing new teeth from the same self-renewing cellular material out of which much of the embryonic human body creates itself was theoretically doable.
It would simply be a matter of one day harvesting stem cells from human wisdom or baby teeth, spurring the growth of new teeth in a lab, and introducing the life-giving substance to a human mouth.
“I have no doubt that whole teeth regeneration is going to happen one day,” Professor Bartold said at the time.
The project was done in collaboration with a leading dental stem cell researcher from the University of Southern California, Dr Songtao Shi.
In 2009, Dr Shi reported that he had managed to create a living tooth root in a pig but told the media, “we’ve got a long way to go” toward creating a human tooth.
Eighteen years later, the quest continues. In April this year, New Zealand’s Health Minister Jonathan Coleman and Science and Innovation Minister Paul Goldsmith announced the winners of the Health Research Council’s $150,000 Explorer grants, one of whom was University of Otago researcher Dr Azam Ali.
According to the accompanying media release, Dr Ali’s “No drill, no fill” project “will develop a biometric system that can potentially trigger remineralisation and regrowth of dental tissues”.
Dr Ali currently holds 18 international patents and patent specifications for medical devices, many of which have been approved for commercial use in New Zealand, Australia, the US and the EU.
“Whole tooth regeneration in animals [using embryonic tooth germ cells] has been successfully achieved by research groups in Japan and the UK. But it will be some time before this becomes a reality for human teeth.”—Professor Mark Bartold, The University of Adelaide
But it looks like we’ve still got a while to wait before human tooth regeneration reaches commercial proportions.
Bite caught up with Professor Bartold in September this year. He was optimistic that his earlier project had demonstrated the potential for growing teeth based on animal studies, but he acknowledged that we’re still a ways away from making the leap to humankind.
“We completed a number of studies in large and small animals, each of which demonstrated that autogenous, allogeneic and MSC derived from iPS cells could result in periodontal regeneration,” Professor Bartold said.
“Whole tooth regeneration in animals [using embryonic tooth germ cells] has been successfully achieved by research groups in Japan and the UK. But it will be some time before this becomes a reality for human teeth.
“The obstacles are many and complex, and they include the development of stringent, good manufacturing procedures for clinical translation and safety and efficacy questions,” Professor Bartold said. “Finally and most importantly, cost will be a huge issue as these processes are very expensive and it is difficult to see how these costs can be significantly reduced.”
Dr Munira Xaymardan of The University of Sydney—an oral and maxillofacial surgeon whose research areas include cardiac stem cells, tissue engineering and embryology—takes a similar view, though she told Bite that the extensive research around tooth regeneration involving stem cells “has given a lot of insight into how teeth generate in the first place”.
That insight will certainly help any future success of whole tooth regeneration, but for now the obstacles to growing human teeth remain formidable, Dr Xaymardan said.
“You can get components of the tooth structure, but I think there’s still a very long way to go achieving the generation of an anatomically and functionally viable human tooth.”
Stem cell research has enabled medical science to “extend the reparative capacity” of human body parts including teeth, but with full tooth generation each patient would pose its own set of challenges, making the costs of treatment prohibitive.
“If you wanted to regenerate a tooth tailored to an individual, it would simply cost too much,” Dr Xaymardan said.
Nevertheless, the obstacles may be coming down bit by bit as genetic modification of cells becomes increasingly possible and stem cell science edges closer to a standardised approach for a given medical procedure.
“I’ve been involved in stem cell regenerative studies since 2004,” Dr Xaymardan said. “The tooth is a little bit different from the other tissues in the human body, but in general we are moving toward a one-for-all approach in the case of stem cell-based regeneration, and it’s a very promising field of research. If we can overcome the immunogenic obstacles [in which the human body rejects the introduction of foreign biological material] and establish a one-for-all approach, growing human teeth on a scale that could change dentistry as we know it is a real possibility, but not an immediate one.”
Of course, it’s not hard to imagine that the huge and highly profitable international industry built up around supplying dental prosthesis materials to practitioners will not be stepping up to fund dental regeneration projects anytime soon.
In 2015 the Australian dental implant and prosthesis market stood at USD$35.8 million. That figure is expected to grow to over USD$50 million by 2020.