In regenerative therapy, stem cell transplantation therapies have been developed to treat organ dysfunction due to injury or disease. The ultimate goal of regenerative therapy is to achieve organ replacement using regenerative therapies by developing fully functioning bioengineered organs. In the dental field, therapies for the missing teeth have already been established such as bridge and implant therapy. In addition, "tooth regeneration", which involves a process of regenerating a tooth by reconstituting bioengineered tooth germ, has been developed, and researches for regenerative medicine has made the most progress in teeth. Recently, we developed a bioengineering method for forming three-dimensional tooth germ that could generate a complete tooth from dissociated single tooth germ cells. The bioengineered tooth germ was shown to generate a structurally correct tooth in a tooth cavity in vivo. Regeneration of the entire tooth requires further researches for development of technologies such as generating a tooth by using stem or precursor cells from patients, controlling tooth morphology, and shortening the treatment period. Also, researches into tooth regeneration will provide basic techniques that may possibly be applied for other organs, and such researches are expected to be propelled as the useful model for the consideration of strategies in future organ replacement therapies.

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The purpose of this study was to evaluate the novel graft material for sinus augmentation by controlled release of basic fibroblast growth factor (bFGF) and biodegradable ceramics. We grafted following 4 materials into frontal sinus of beagle dogs. 1. β-tricalcium phosphate (β-TCP) and bFGF-incorporated gelatin hydrogel microspheres, 2. β-TCP and physiological saline-incorporated gelatin hydrogel microspheres, 3. β-TCP and bFGF solution, and 4. autologous bone. Augmented bone was evaluated by soft X-ray, histlogical examination and histomorphological examination at 4 and 12 weeks after implantation. When the β-TCP and bFGF-incorporated gelatin hydrogel microspheres were grafted, newly formed bone tissue volume was larger than other groups. This finding indicated that bFGF-incorporated gelatin hydrogel microspheres enables to effectively increase bone formation. We concluded that β-TCP and bFGF-incorporated gelatin hydrogel microspheres was a novel promising graft material for sinus augmentation, since it can be easily prepared and does not require a autologous bone harvest.

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The present study aimed to conserve dentin by rehardening demineralized root canal dentin which is completely removed during endodontic and/or prosthetic therapy as a general rule. Numerous previous studies have reported that hydroxyapatite (HA) is highly biocompatible in dentistry, does not hinder the body's healing ability, and possesses the ability to facilitate recalcification and hard tissue guidance. Therefore, HA was used in the present study.
As an underlying experiment, demineralized root canal dentin was artificially prepared. Nano-HA was applied to root canals, and subsequent rehardening of demineralized dentin was observed. Furthermore, rehardening was observed in the deep layer of root canal dentin.
By allowing nano-HA to act on root canals for a certain period of time, natural dentin strength could be regained, thus suggesting the possibility that demineralized root canal dentin that is removed during prosthetic therapy may be conserved in the future.

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