Teeth: an organ with crucial functions
Chewing is not all that teeth do. They shift with age and transmit sensory stimuli via their connections with the periodontal ligament, the connective tissue that anchors them to the jawbone. Modern dental therapy tends to involve replacing lost or damaged teeth with functional replacements, usually prosthetic devices such as dentures, bridges, and oral implants. While prosthetics indisputably help restore patients’ chewing ability, they fall short when it comes to other biological functions such as shifting and sensory perception. This shortcoming has sparked interest in developing new therapeutic technologies in dentistry capable of restoring the full physiological functionality of natural teeth.
Tooth regeneration: a revolution in complete functional restoration
Humans have two sets of teeth: milk and permanent. These originate from two distinct types of primordial dental tissue (or germ), which are induced by interactions between epithelial and mesenchymal stem cells during fetal development. Their early origin means that once a permanent tooth is lost, a new one will not grow to replace it. However, this may soon be a thing of the past, thanks to our revolutionary new tooth regeneration technology. First, new dental germ is grown outside the body using the organ germ method. When transplanted to the site of the missing tooth, budding is induced until a fully functional tooth regrows in its place. This is a huge breakthrough in dental research, of the likes not seen for over 30 years. Teeth regrown using this approach possess a periodontal ligament, nerves, and vasculature, just as in natural teeth, demonstrating the feasibility of functional restoration. Recently, we achieved success in a dog model, observing canine tooth regrowth after transplanting permanent tooth germ to the site of a lost tooth. Human applications could soon be a reality.
However, before this can happen, it is crucial to identify suitable seed cells that can be harvested from patients for the procedure. To this end, we are currently screening different types of tooth germ and stem cells, and exploring how to induce tooth germ and periodontal tissue from induced pluripotent stem cells, in several ongoing research studies.
The near future holds revolutionary dental treatments and next-generation implants
Modern oral implants present a range of problems. Since they are embedded directly into the alveolar bone, they are poorly suited to patients with low bone volume. Since they lack a periodontal ligament, they cannot shift normally in the same way as natural teeth. Likewise, they are inappropriate for younger patients, whose jawbones are still growing as part of normal development. Patients may experience looseness due to insufficient anchoring to the bone, and bacterial infection, implant damage, and other treatment-related issues have been widely reported. Long-suffering users are eagerly awaiting a new generation of innovative implant treatments that can improve this state of affairs. Most of the problems mentioned above can be attributed to a lack of normal periodontal tissue around the site, including the periodontal ligament, which connects teeth to the alveolar bone in unaffected individuals. To resolve them, we are currently developing a next-generation “biohybrid” oral implant that is already connected to periodontal tissue and designed to have the same functionality as the natural dental root.
Making next-generation implants a reality
We thought the major issues with implants above could be overcome if they could be made identical to natural teeth in terms of their physiological functionality. The periodontal ligament is critical in this regard. If an implant were indirectly connected to the bone via this structure, it could solve all of these issues at once.
We tested our idea by applying tissue taken from the dental follicle—a cell population in the dental germ that gives rise to periodontal tissue—to a hydroxyapatite-coated implant, and transplanting it into the jawbone of a model mouse for tooth loss. What formed was unmistakably periodontal tissue, characterized by distinct layers of cement, ligament, and alveolar bone extending from the implant surface. Nerve fibers had even spread into the area, restoring sensory innervation. We had successfully created a next-generation dental implant capable of regrowing healthy periodontal tissue. In addition, since it is the periodontal tissue that mediates the ability of teeth to shift, our invention is even suitable for orthodontic treatments.
Research and development continues unabated: we have shown subsequently that it is possible to attach the periodontal ligament to implants immediately after teeth are removed, and successfully developed a technique to create implants using patients’ own ligament cells. We are working on establishing clinical applications for our next-generation implants as soon as possible, to improve the public’s health and quality of life.