Recently, the frequency of use of bone substitute materials for the purpose of bone augmentation has increased in implant treatment, but bone formation with bone substitute materials alone is limited. Calcification of bone in the body progresses as Ca²⁺, H₂PO^4-, and HPO₄^2- in the body form hydroxyapatite (HA) crystals. In this study, therefore, we prepared a biphasic bone substitute with biological activity to promote bone formation by inducing precipitation and growth of HA crystals on the surface of a bone substitute and evaluated it. Biphasic bone substitute granules were prepared by immersing HA granules in a supersaturated calcium phosphate solution prepared by mixing five medical infusion solutions, the precipitate was analyzed, and the biological activities of biphasic HA granules were evaluated in vitro and in vivo. As a result, the precipitated calcium phosphate crystals were identified as low crystalline HA. On the surface of the HA granules, low-crystalline HA grew markedly as needle-shaped crystals and significantly promoted cell proliferation and bone differentiation. In animal experiments, biphasic HA granules had a significantly higher bone mineral density, new bone volume ratio, and new bone area ratio. Therefore, it suggests that biphasic hydroxyapatite is a useful bone substitute for bone augmentation in dental implant treatment.

In this study, using electrolytic reducing ionic water (S-100^®), a novel surface treatment method safely and easily modifying the surface properties was evaluated in vitro and in vivo. Ti-6Al-4V disks were washed and the disks were kept standing on a clean bench for one and four weeks for aging. These disks were immersed in S-100^® (S-100 group), immersed in ultra-pure water (Control group), or irradiated with ultraviolet light (UV group), and surface analysis, cell experiment, and animal experiment were performed using these disks. The titanium surface became hydrophilic in the S-100 group and the amount of protein adsorption and cell adhesion rate were improved in vitro. In vivo, new bone formation was noted around the disk. These findings suggested that surface treatment with S-100^® adds bioactivity to the biologically aged titanium surface. We are planning to further investigate it and accumulate evidence for clinical application.

This study aimed to investigate the effects of aspirin on the early stages of odontogenic differentiation. The roles of FOXC1, RUNX2, and MCAM gene expression in the mechanism of odontogenic differentiation were evaluated by examining the effects of downregulated FOXC1 or RUNX2 expression using small interfering RNAs (siRNAs). Dental pulp cells were treated with aspirin (0, 2.5, 50, 100 μg/ml) to assess its impact on mineralization. The gene expression levels of FOXC1, RUNX2, and MCAM were measured using digital polymerase chain reaction, and the effects of siRNA-mediated knockdown of FOXC1 and RUNX2 were analyzed. The mineralization potential was quantitatively assessed using Alizarin Red S staining and a calcium assay. Analysis of cell growth curves and doubling times indicated that aspirin did not affect cell proliferation at 2.5 μg/ml and 50 μg/ml; however, 50 μg/ml aspirin promoted mineralization. In the FOXC1 and RUNX2 knockdown experiments, fluctuations in FOXC1, RUNX2, and MCAM gene expression were observed in the aspirin-treated group, suggesting the involvement of these genes in mineralization. Alizarin red S staining and calcium assays further demonstrated that aspirin enhanced mineralization. These findings indicate that aspirin promotes odontogenic differentiation and regulates the expression of FOXC1, RUNX2, and MCAM. This suggests that aspirin may serve as a promising new therapeutic agent in dental pulp regenerative medicine.

Patient-specific cutting guides are used for safe and accurate jaw resection during oral and maxillofacial surgery. This study investigated the effect of shavings from 3D-printed cutting guide materials during surgery on bone healing. The biocompatibility of commercially available biocompatible polymers including photopolymer resin (PP) and polyamide resin (PA) materials was assessed in the present study. The viability of mouse osteoblast-like MC3T3E-1 cells was evaluated upon coculture with the materials. Furthermore, the effects of PP and PA as additives on bone formation were investigated in a rat calvarial bone defect model. Both PP and PA were biocompatible and allowed cells to attach to them. However, both materials could be damaged when cutting devices were used, and their shavings impaired osteoblast proliferation and bone formation. Cutting guide materials are designed to be biocompatible when they are fabricated according to the manufacturer’s protocol. Nevertheless, the polymer shavings generated during jaw cutting might adversely affect bone healing.