Dental regeneration is to restore a tissue defect to its original form and function by biological substitutes. The possible experimental approaches to the creation of a dental prosthesis include scaffold based approach, cell aggregation based approach and stem cell homing based approach (see Fig. 6.4) . Dental repair is by metal or artificial materials whereas regeneration is by biological restoration . Ideally, biomaterial scaffolds in tooth regeneration should be biocompatible, be nontoxic, undergo biologically safe degradation, provide encapsulation of cells or surface adhesion for cells, and allow functionality of cells including ameloblasts, odontoblasts, cementoblasts, fibroblasts, vascular cells and neural endings . Several classes of materials have been used for dental tissue engineering, such as PLGA, PLA and hydroxyapatite/tricalcium phosphate (HA/TCP) .
Damage of teeth, such as caries, dental wear lesions or trauma can result in rupture of the apical blood vessel network and dental pulp necrosis. Dental pulp therapy is currently limited to conventional restorations such as root canal therapy which allows for infection control, but does not facilitate the completion of root formation and protection against external root resorption. Dental pulp tissue engineering including potential cell sources and biocompatible materials have been considered an attractive strategy for dental pulp regeneration . Responsive cells are generally stem cells. Dental pulp stem cells, which is therapeutically employed for direct and indirect pulp capping, are capable of differentiating into odontoblast-like cells or ECs. In addition, dental pulp stem cells have the lifelong regenerative cability and the potential to continue root development in necrotic immature teeth and trans- planted/replanted teeth . Studies in dental biomaterials research aim at the development of suitable biomimetic and degradable biomaterials with uniquely functional properties at a nanometer-scale. A variety of scaffolds, such as collagen, polyester, chitosan, or hydroxyapatite has been investigated. Self-assembling peptide hydrogels are an example of a smart material that can be modified to create customized matrices . Pulp tissue is not particularly conducive to the rapid and effective vasculogenesis. VEGF is the prototypic pro-angiogenic factor. It could enhance the neovascularization of severed human dental pulps .
An ideal regenerative protocol would primarily include root decontamination with antimicrobial irrigant solutions, followed by insertion of a more cell-friendly bioactive scaffold containing antimicrobial substances to be released inside the canal. Once a bacteria-free environment conducive to tissue regeneration has been established, scaffolds containing growth factors and/or stem cells would be placed to induce development of a new pulp tissue containing odontoblasts that will form dentin-like tissue . The new engineered pulp tissue could generate new dentin and establish tooth function, which is a critical step forward in the process of translating the concept of dental pulp tissue engineering to the clinic .