Tooth Germ‐Like Construct Transplantation for Whole‐Tooth Regeneration: An In Vivo Study in the Miniature Pig

Abstract

The purpose of this study was to demonstrate the feasibility of whole-tooth regeneration using a tooth germ-like construct. Dental pulp from upper incisors, canines, premolars, and molars were extracted from sexually mature miniature pigs. Pulp tissues were cultured and expanded in vitro to obtain dental pulp stem cells (DPSCs), and cells were differentiated into odontoblasts and osteoblasts. Epithelial cells were isolated from gingival epithelium. The epithelial cells, odontoblasts, and osteoblasts were seeded onto the surface, upper, and lower layers, respectively, of a bioactive scaffold. The lower first and second molar tooth germs were removed bilaterally and the layered cell/scaffold constructs were transplanted to the mandibular alveolar socket of a pig. At 13.5 months postimplantation, seven of eight pigs developed two teeth with crown, root, and pulp structures. Enamel-like tissues, dentin, cementum, odontoblasts, and periodontal tissues were found upon histological inspection. The regenerated tooth expressed dentin matrix protein-1 and osteopontin. All pigs had regenerated molar teeth regardless of the original tooth used to procure the DPSCs. Pigs that had tooth germs removed or who received empty scaffolds did not develop teeth. Although periodontal ligaments were generated, ankylosis was found in some animals. This study revealed that implantation of a tooth germ-like structure generated a complete tooth with a high success rate. The implant location may influence the morphology of the regenerated tooth.

The Current Status of Stem Cell Regeneration in Intra Oral Applications—A Systematic Review

“…Angelova Volponi et al reported success using adult gingival epithelial cells, which upon recombination with mesenchymal cells generate mature teeth and form enamel and dentin [137]. Similarly, Yang et al generated a complete tooth by implantation of a tooth germ like structure in animal models [138].…”

Progress in Bioengineered Whole Tooth Research: from Bench to Dental Patient Chair

“…PLLA, PLGA and their derivatives are synthetic polymers that can be readily prepared. Hydrogel based materials such as collagen, gelatin, and alginate are highly tunable, and have been used to successfully bioengineer various dental tissues [21, 22, 32, 52]. Silk-based materials have also shown promise in providing an environment that can support osteo-dentin like mineralized tissue formation, but further optimizations are needed to enhance bioengineered dental tissue formation [53, 54].…”

“…Decreased FGF signaling prevents tooth development [71, 72]. TGFβ1 can induce odontoblast differentiation, pulp and dentin formation [73–76], and has been used to enhance the differentiation DPSCs into odontoblasts in vitro [21]. These studies emphasize that selective incorporation of combinations of these growth factors into novel bioengineered tooth constructs could be used to enhance dental cell differentiation, and dental tissue and whole tooth formation.…”

“…Mini-pigs are commonly used for tooth/alveolar bone implantation studies because they have a dentition similar to humans. [77, 78] It has been suggested that the implantation site is important as it may influence the morphology of the bioengineered tooth [21]. Therefore, knowing how, when and where to place the bioengineered tooth implant can greatly affect its outcome.…”

“…Since then, additional studies have focused on identifying appropriate sources of adult dental cells, on appropriate and optimal scaffold materials, and on growth factor combinations that can properly direct the regeneration of functional bioengineered tooth. A recent report describes the use of a gelatin-chondroitin-hyaluronan scaffold seeded with postnatal dental cells implanted into a healed mandibular tooth extraction site of an adult Lanyu miniature pig, to successfully generate enamel-like tissues, dentin, cementum, and developing tooth roots [21] •• . Further improvements to this model, including validation that the purported bioengineered tooth was in fact not a natural pig replacement tooth, as well as functional analysis of these bioengineered teeth, would significantly improve the significance of this study.…”