Enamel Tissue Engineering

Dental scientists are eagerly embracing regenerative medicine using tissue engineering technology. Enamel, one component of teeth, is the hardest tissue in the body. It cannot regenerate by itself, because it is formed by a layer of ameloblasts that is lost by the time the tooth crown has completely formed. Although the enamel is spent during lifetime, it is vulnerable to wear, damage, and decay. For these reasons, the development of a technique that produces artificially-grown enamel using culture and transplantation techniques is strongly desired. In this chapter we report a new technique for culturing enamel organ epithelial cells that have the capacity to produce enamel. After completion of the formation of the tooth crown, which is composed of an enamel-dentin complex, tooth root formation begins. Generally, no new ameloblasts or enamel is generated from the enamel organ epithelial cells after the tooth root is formed. Epithelial cell rests of Malassez, derived from Hertwig’s epithelial root sheath fragments, are located in the periodontal ligament, and recently we reported that these cells are also capable of enamel production using the same technique. Dental epithelial cells including enamel organ epithelial cells and epithelial cell rests of Malassez can continue to proliferate when they are subcultured on top of feeder layer cells. These subcultured cells were placed onto collagen sponge scaffolds along with dental pulp cells and the constructs were transferred into the abdominal cavities of rats. When removed after 4 weeks, enamel production was observed in the scaffolds. The key finding of this study is that even after multiple divisions, the cells retained the capacity to produce enamel. Now that dental epithelial cells can be generated by a culture and transplantation system, the next step will be to combine the tissue-engineered enamel with the injured enamel in original teeth.