Regenerative medicine is expected as a new medical system for the 21st century. The major goal of dental care in the future is tooth regeneration treatment to regain lost teeth by regeneration. Previously, we developed an Organ Germ Method, a three-dimensional cell manipulation technology, and made it possible to regenerate fully functional teeth such as the periodontal ligament and neural functions by orthotopic transplantation of regenerated a bioengineered tooth germ. As a restoration of teeth that will restore full function as a dental treatment of the future, it is possible not only to transplant regenerated bioengineered tooth germ, but also to regenerate functional teeth that do not become dental caries by imparting the periodontal ligament to the current osseo-integrate implant treatment. As a next-generation implant treatment, we have developed a biohybrid implant that has periodontal tissue and expresses the physiological functions of teeth. In addition, we are developing implant material and examining non-clinical efficacy using large animals. In this paper, we introduce the strategy and progress of research for the realization of dental regenerative medicine as a dental treatment in the future.

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Based on the remarkable progress of researches in the fields of tissue engineering and regenerative medicine, the possibility of cell therapy using cultured cells for various diseases and dysfunctional tissues has been widely suggested. In the field of dentistry, many studies have been conducted, aiming to develop new cell-based therapies for various diseases such as regeneration of oral tissues, periodontal diseases, pulpitis, mucosal diseases, and salivary gland diseases. We have examined the possibility of periodontal tissue regeneration by cell transplantation and demonstrated the utility of cell sheet technology for the regeneration of periodontal tissues as a simple and reliable method of cell transplantation. Furthermore, periodontal tissue regeneration on the surface of titanium implants was also verified using this technique. In this review, we outline cell sheet technology and its potential for construction of implants with periodontal tissues.

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Herein we focused on NANOZR, which has high fracture toughness and elasticity, to create a new implant material by applying surface structure control via concentrated alkali treatment. We investigated the initial adhesion of bone marrow cells and the ability of this material to induce hard tissue differentiation. Two experimental samples were used: NANOZR treated with a concentrated alkali at room temperature and titanium treated with an alkali solution. A commercially available NANOZR plate with a mechanically polished surface was used as a control. Analysis was performed using scanning electron microscopy (SEM) and scanning probe microscopy (SPM), as well as X-ray photoelectron spectroscopy (XPS) for surface analysis. In addition, the contact angle of distilled water on the surface of each group was measured, and the initial adhesion of bovine serum albumin was investigated. After bone marrow mesenchymal cells were collected from the bilateral femurs of 7-week-old male Sprague-Dawley rats, a primary culture was established, and the third generation was used for the experiment. We also measured alkaline phosphatase activity at 14 and 21 days after culturing, the amount of osteocalcin produced, and the amount of calcium precipitated after 21 and 28 days. In addition, the expression of gene markers related to differentiation induction was examined from the mRNA obtained after reverse transcription from the cells 3 days after culture. Observation using SEM and SPM showed that a nanometer-level network structure was formed on the alkali-treated titanium, but there was no change in the NANOZR. In XPS observations, it was found that a deep oxide film layer was formed on the alkali-treated titanium and alkali-treated NANOZR. The expression of various differentiation-inducing markers and gene markers was higher in the experimental group than in the control group at all measurement times, and there was no difference in the values between the alkali-treated titanium and the alkali-treated NANOZR. Based on the above results, it is suggested that nano-level surface modification may be useful for improving the differentiation-inducing ability of bone marrow cells in alkali-treated NANOZR, similar to the case of titanium.

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Diet restriction and fasting could promote tissue regeneration and enhance the immune system by increasing the number of stem cells in the body. Thus, temporary restriction of nutrients at a cellular level may affect its proliferation or differentiation capacity. The present study aimed to investigate and evaluate the effect of glucose reduction and recovering (GRR) regimens on mouse bone marrow cells (BMCs). BMCs were extracted from femurs of 17-week-old male CB57L/6 mice and were grown in a 24-well plate. Then, the cells were divided into 3 groups: intermittent GRR (IGRR), prolonged GRR (PGRR), and control (C), each with (+) or without (–) osteogenic supplements. After 2 weeks of GRR regimens, cell proliferation was measured, osteogenic differentiation was evaluated by an alkaline phosphatase (ALP) activity assay and mineralized nodule staining, and mRNA expression reflecting osteoblast differentiation was evaluated by reverse-transcription quantitative polymerase chain reaction. Cell proliferation significantly increased in IGRR+/- and PGRR+/- cells than in C+/- cells. There was a significant increase in ALP-positive cells and mineralized nodule formation as well as in the gene expression of alkaline phosphatase (ALP), Bone Morphogenetic Protein-2 (BMP-2), Osterix (OSX), and Osteocalcin (OCN) in PGRR+ cells. However, IGRR+/- and PGRR- cells did not show a significant difference in those genes when compared to C+/-. Both IGRR and PGRR enhanced cell proliferation. Moreover, PGRR+ promoted osteoblast differentiation of BMCs in vitro, whereas IGRR+ did not show any positive effects on osteogenic differentiation of BMCs. Conclusively, GRR, especially PGRR, enhanced osteoblast proliferation and upregulated gene expression of ALP, BMP-2, OSX, and OCN.

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