Several different types of stem cells can regenerate tooth enamel, but regenerating the tooth root has proven quite difficult.
As you can see from the image above, the tooth root is covered with a tough, fibrous covering called the cementum. The cementum connects the tooth root to the alveolar bone of the upper and low jaw by means of the periodontal membrane. the cementum is a thin layer of bone-like material that covers the roots. It is yellowish and softer than either dentine or enamel. It is made by a layer of cementum-producing cells called cementoblasts that are adjacent to the dentine. The periodontal ligament is cellular and its fibers hold the tooth in its socket, which are embedded in the cementum, as shown in the micrograph below. The complexity of this structure shows you why regenerating this structure is so difficult.
Howwever, a new study from the laboratory of Weihua Guo at Sichuan University, China has shown that platelet-rich fibrin (PRF) and treated dentin matrix (TDM) can concentrate a variety of various growth factors that summon native stem cells to them, and induce them to regenerate the tooth root.
Guo’s laboratory examined the ability of PRF and TDM to summon endogenous stem cells to the site of an extracted tooth in order to initiate regeneration of the tooth root. Tooth roots contain soft and hard periodontal tissues, and if periodontal ligament stem cells (PDLSCs) and bone marrow mesenchymal stem cells (BMSCs) could be recruited to the site of tooth extraction by PRF and TDM, then maybe they could initiate tooth root regeneration.
Beagles were used as a transplantation model for this experiment. After tooth extraction PRF and TDM implants were embedded in the tooth socket. Also, these matrices were examined in cell culture with PDLSCs and BMSCs.
PRF significantly recruited and stimulated the growth of both PDLSCs and BMSCs in culture. In combination, PRF and TDM induced cell differentiation of these implanted stem cell populations. PRF and TDM induced the expression of mineralization-related genes, such as bone sialoprotein (BSP) and osteopotin (OPN) after only one week in culture.
When implanted into the tooth sockets of beagles that had teeth extracted, transplantation platelet-rich fibrin made from the dog’s own blood products, and TDM made from other animals into fresh tooth extraction socket successfully regenerated the tooth root 3 months after the surgery. The cementum and periodontal ligament (PDL)-like tissues with properly orientated fibers were clearly present, and the presence of these structures is indicative of functional restoration.
These results suggest that tooth root and the connection of the tooth root to the alveolar bone by cementum and peridontal ligaments can be effectively regenerated through the implantation of PRF and TDM in a tooth socket. It seems to achieve this regeneration by summoning BMSCs and PDLSCs. These cues provided by these matrices and the microenvironment provided by the tooth socket are key factors for this regeneration. This strategy provides a genuine clinical pathway toward tooth root regeneration in human patients with destroying human embryos.