Kazuhiro Kon

Bone augmentation ability of autogenous bone graft particles with different sizes: a histological and micro-computed tomography study.

OBJECTIVES The purpose of this study was to investigate the augmentation process and ability of autogenous bone graft particles of two different sizes in a vertical augmentation chamber. MATERIAL AND METHODS The cranial bones of 24 rabbits were used. Two polytetrafluoroethylene chambers were filled with harvested bone from tibia with small bone (SB; 150-400 microm) and large bone (LB; 1.0-2.0 mm) of the same weight. Animals were sacrificed after 1, 2, 4 and 8 weeks. The samples were analyzed by micro-computed tomography (micro-CT) for quantitative analysis, and embedded in polyester resin as non-decalcified specimens for histological analysis. Total bone volume (TBV), bone height (BH) and distribution of bone structure were calculated by micro-CT. RESULTS Micro-CT evaluation and histology revealed a significant difference between the investigated specimens. TBV and BH of SB decreased to about 50% of the initial situation, and there was a statistically significant difference between 1 and 8 weeks. In contrast, TBV and BH of LB were almost retained at all experimental time points. Significant differences in TBV and BH were also observed between LB and SB at 8 weeks. Bone volume of SB decreased predominantly in the upper half of the chamber at 4 and 8 weeks. In the histological observations, SB showed favorable new bone formation and rapid bone resorption in a time-dependent manner during the entire experimental period. However, LB exhibited favorable morphological stability and continued new bone formation. CONCLUSION SB follows a smooth osteogenic process, whereas it is not effective in volume augmentation. LB is superior to SB in augmentation ability.

Differentiation of Bone Marrow Stromal Cells into Osteoblasts in a Self-assembling Peptide Hydrogel: In Vitro and In Vivo Studies

A prerequisite of tissue engineering approaches with regard to autograft is a suitable scaffold that can harbor cells and signals. Conventionally, such scaffolds have been prepared as 3D scaffolds prefabricated from synthetic or natural biomaterials. RAD16 has been introduced as a new biomaterial, where synthetic peptides self-assemble to form a hydrogel. In this study, RAD16 was examined in terms of osteogenic efficacy and feasibility of ectopic mineralization. Two hundred and seventy-one RAD16 was cocultured with 1 × 106 bone marrow cells from the femurs of 6-week-old Wistar male rats in alpha minimum essential medium supplemented with or without dexamethasone. Second, the same volume of the RAD16 construct hosting the cells with or without hydroxyapatite (HA) particles was treated in the dexamethasone medium as well, prepared in a Teflon tube, and implanted subcutaneously. Cell proliferation was prominent in the RAD16 coculture with dexamethasone at 1 week and significantly decreased by 2 weeks, whereas the other combinations remained or inclined, and their osteogenic differentiation was accelerated up to 2 weeks, as seen in increasing alkaline phosphatase (ALP) activity and mRNAs of ALP, OPN, and OCN. The RAD16 implant prepared with HA particles allowed more osteoblast-like cells and blood cells to grow inside, which was accompanied by elevating OPN gene expression and the stronger peak of VEGF gene expression at 2 weeks. Furthermore, more OPN mRNA signal was detected around the RAD16 containing HA particles by 4 weeks. On the other hand, the RAD16 alone represented lower expression of OPN gene. During the experiment, however, no ectopic mineralization was observed in both groups. Conclusively, it was suggested that the RAD16 showed feasibility of serving as a matrix for osteogenic differentiation of cocultured bone marrow cells in vitro and in vivo. Proceeding of exploration and modification of RAD16 are continuously required for cell-based tissue engineering.

Evaluation of a biodegradable novel periosteal distractor.

UNLABELLED We developed a new device composed of a thin biodegradable mesh (poly-L-lactide/hydroxyapatite composite) for distracting periosteum. The purpose of this study is to evaluate the effect of using this device as a periosteal distractor. MATERIALS AND METHODS Eight Japanese male rabbits were divided into two groups according to time of sacrifice. The calvarial periosteum was elevated and one side of a biodegradable mesh was fixed to the bone surface with two titanium screws. Seven days after the surgery, an elevating screw was inserted into the other side of the mesh. Then, the calvarial periosteum was elevated at maximum 0.5 mm every 12 h for 5 days. The device was designed to distract the periosteum at different rates along its entire surface. At 4 and 6 weeks of the consolidation, the animals were sacrificed and newly formed bone was histologically and radiographically evaluated. RESULTS The new device simplified periosteal distraction and reduced its invasiveness. Moreover, it successfully induced new bone formation from two sources; the periosteum and the underlying basal bone. Histomorphometric analysis of the distracted space showed that there is a relation between the rate of distraction and the amount of newly formed bone. We suggest that the optimal speed range for periosteal distraction in rabbit calvarial model could be less than 0.33 mm/day. CONCLUSIONS The new device is slim, biodegradable and the procedure is simple. Thus, periosteal distraction with this device is potential for vertical and horizontal ridge augmentation in oral cavity.

The effect of graft bone particle size on bone augmentation in a rabbit cranial vertical augmentation model: a microcomputed tomography study.

PURPOSE The purpose of this study was to investigate the impact of graft bone particle size on autogenous bone graft augmentation in a vertical augmentation chamber model. MATERIALS AND METHODS A total of 12 rabbits were used in this study. The donor bone particles were of different sizes: small (150 to 400 μm), large (1.0 to 2.0 mm), and a mixture comprising equal weights of both large and small bone particles. One type of bone graft material was placed into each of two polytetrafluoroethylene chambers that were implanted in the parietal bone of each rabbits cranium. Animals were sacrificed 4 or 8 weeks after the grafting procedure. The recovered samples were analyzed by microcomputed tomography (micro-CT) for quantitative analysis. Total bone volume, bone height, and the distribution of bone structure were calculated by micro-CT. RESULTS Micro-CT evaluations revealed that the bone grafts performed with large bone particles provided, statistically, the best outcome. Total bone volume and bone height decreased in a time-dependent manner, and there was a statistically significant reduction in total bone volume between 4 and 8 weeks in the group with the mixed bone particle sizes. CONCLUSION Within the limitations of the present study, large bone graft particles provided the best preservation of total bone volume and bone height up to 8 weeks after grafting in an animal vertical augmentation model.