Makoto Shiota

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.

Exploitation of a novel polysaccharide nanogel cross-linking membrane for guided bone regeneration (GBR).

Cholesterol‐bearing pullulan (CHP) nanogel is a synthetic degradable biomaterial for drug delivery with high biocompatibility. Guided bone regeneration (GBR) is a bone augmentation technique in which a membrane is used to create and keep a secluded regenerative space. The purpose of the present study was to evaluate the effects of the novel CHP nanogel membrane in GBR. Thirty‐six adult Wistar rats were used and bilaterally symmetrical full‐thickness parietal bone defects of 5 mm diameter were created with a bone trephine burr. Each defect was covered with the collagen membrane or the CHP nanogel membrane or untreated without any membrane. The animals were sacrificed at 2, 4 and 8 weeks and analysed radiologically and histologically. Furthermore, after incubating human serum with CHP nanogel or collagen, the amount of PDGF in the serum was measured using ELISA. New bone formation in terms of bone volume was higher in the nanogel group than in the control or collagen groups at 2 and 4 weeks. At 8 weeks, both membrane groups showed higher bone volumes than the control group. Notably, the newly‐formed bone in the bone defect in the nanogel group was uniform and histologically indistinguishable from the original bone, whereas in the collagen group the new bone showed an irregular structure that was completely different from the original bone. After incubating with CHP nanogel, the amount of PDGF in the serum decreased significantly. CHP nanogel GBR membrane favourably stimulated bone regeneration, in which a unique characteristic of CHP nanogel, the storage of endogenous growth factors, was likely implicated. Copyright

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.

Failure analysis of an abutment fracture on single implant restoration.

Purpose:This study evaluated the mechanism of an abutment fracture by means of a case-based finite element (FE) stress analysis. Materials and Methods:A patient presented with a complaint of fracture of an implant-retained single posterior restoration that had been in place for 6 years. The retrieved restoration was examined on the original working cast and subjected to microscopic observation for fracture surface analysis. A case-based FE analysis was conducted to detect the location and magnitude of stress concentration in the implant structures. Results:The fracture occurred at the concave neck of the abutment, with an evidence of fatigue fracture on the titanium surface. Ratchet marks were shown at the distal lingual edge, indicating that the crack proceeded from distolingual to mesial direction. The highest maximum tensile stress at the distolingual concave neck of the abutment was shown when the load was directed on the internal and external surfaces of the mesial buccal cusp. Conclusions:It is suggested that an offset loading because of the cantilever structure caused a high tensile stress on the distolingual edge, resulting in the fatigue fracture of the abutment.

Effect of strontium ions on calcification of preosteoblasts cultured on porous calcium- and phosphate-containing titanium oxide layers formed by micro-arc oxidation.

Strontium (Sr) ions were added to calcium- and phosphate-containing porous titanium oxide layers formed by micro-arc oxidation (MAO) of titanium (Ti) substrates to improve their osseointegration. An MC3T3-E1 preosteoblast was used to evaluate the effect of the incorporated Sr species on cell calcification. Similar surface microporous morphologies of the oxide layers were observed for all specimens produced by MAO, while the contents of the incorporated Sr ions increased with increasing Sr concentrations in MAO electrolytes. The calcium- and phosphate-containing porous layers promoted the cell alkaline phosphatase (ALP) activity, while cell calcification was promoted by the Sr addition. In particular, the ALP activity significantly increased after 10 days of culture, and larger areas of calcified deposits were observed for the specimens treated with MAO electrolytes containing 0.15 mol L(-1) of Sr species. The effect of Sr addition on the calcification of the MAO-treated Ti oxide layers was established in this study.

Ten Years Follow-Up of Sputtered Hydroxyapatite Coated Implant in Single or Two Missing Teeth Replacement

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