Toll-like receptor 9 (TLR9) recognizes unmethylated cytosine-guanine dinucleotide (CpG) sequences in DNA and activates immunity by inducing proinflammatory cytokines and interferons. The finding that TLR9 recognizes CpG-DNA is deduced primarily from the results of experiments using DNA with phosphorothioate backbone. Unmethlated CpG sites frequently appear in the DNA of pathogens; they are almost never found in mammalian DNA. Therefore, TLR9 recognition of unmethlated CpG is believed to be related to host defense mechanism. However, proinflammatory cytokines and interferons are also induced by the interaction between TLR9 and DNA consisting entirely of phosphodiester backbone, which multimerize by self-assembly and do not contain CpG. Furthermore, proinflammatory cytokines and interferons are also induced by the formation of complexes of cationic nanoparticles and DNA having only phosphodiester backbone. Therefore, it has now clear that TLR9 recognition of naturally-occurring DNA consisting entirely of phosphodiester backbone does not depend on base sequence. It is possible that TLR9's base sequence-independent recognition of DNA is involved in the activation of not only host defense systems, but also autoimmunity. For activation of autoimmunity by TLR9, it is believed that the formation of biomolecule complexes rather than nanoparticle complexes is involved.

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Penetration through the cell membrane, endosomal escape and nuclear entry are the main barriers that transfection agents have to overcome. We prepared multi-shell calcium phosphate nanoparticles that were functionalized with DNA, polyethyleneimine (PEI) and protamine in order to improve transfection efficiency. PEI-functionalized calcium phosphate nanoparticles showed a high transfection efficiency, which was correlated with cytotoxicity. Additional functionalization with protamine effectively reduced the cytotoxic effects of PEI, while maintaining the high transfection efficiency. Size, surface charge and morphology of multi-shell nanoparticles were analyzed by dynamic light scattering and scanning electron microscopy. The influence of nanoparticle concentration on the transfection efficiency and cell viability was tested on HeLa and MG-63 cell lines. Protamine-functionalized multi-shell calcium phosphate nanoparticles can serve as an efficient and non-toxic gene carrier for cells.

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Orthodontic adhesives are typically colorless and transparent for aesthetic purposes. The utilization of fluorescence is one of the most effective solutions to make the adhesives visible for safe and complete removal after orthodontic treatments. Eu³⁺ ions were doped into yttrium oxides (Y₂O₃) using a homogeneous precipitation method. The crystals synthesized in this study exhibited submicron sizes and a very narrow size distribution. The X-ray diffraction (XRD) patterns agreed well with the known diffraction patterns of Y₂O₃, and indicated an absence of any other crystalline substances. Therefore, it was determined that the crystals synthesized in this study were in fact Y₂O₃:Eu³⁺. The spectra of the poly(methyl methacrylate) (PMMA) adhesives containing Y₂O₃:Eu³⁺ particles exhibited characteristic excitation and emission peaks corresponding to the 4f-4f transitions of Eu³⁺, despite the photoluminescence intensity being relatively low. The yielding loads of the Y₂O₃:Eu³⁺ particles contained in the PMMA specimens did not deteriorate by a significant amount. We conclude that it is feasible to add the Eu³⁺-doped Y₂O₃ crystalline particles into orthodontic adhesives.

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The clinical application of dental zirconia has increased. Adhesion on dental zirconia is important in the usage such as the hybrid type abutment to adhesive to titanium cylinder. For the analysis of surface roughness to influence on various material properties, conventionally the value of depth directions such as the Ra has been widely used. However, the periodicity (wavelength) of roughness in the horizontal direction may also influence adhesive property. The Fourier transform that can perform frequency analysis was effective for the examination of a complicated roughness curve, composed of multiple waves. Shear bond strength test was conducted in the specimen with four kinds of surface roughness (control, low, high, low and high frequency element). Shear bond strength became strong (14MPa) in the specimen with a short wavelength (high frequency element), and weak (4∼5MPa) for a long wavelength (low frequency element). The surface sensitive properties depend not only on the Ra but also on the wavelength. In this study the Fourier transform was effective for various characteristic examinations of surface properties such as the adhesive property and shear bond strength could be better understood by wavelength dependence.

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Dentistry needs new bone substitute materials. The purpose of this study was to prepare nano-hydroxyapatite/collagen composite (n-HAP/Col); and evaluate its usefulness as osteo-conductive bio-material by using animal model. We formed collagen control (Col) and n-HAP/Col specimens of 6 mm width and 1 mm height, by freeze-drying, de-hydrothermal cross-linking and punching. Critical-size bone defects (6 mm) were generated in the cranial bones of thirty-six 10-week-old Wistar rats, in which Col and n-HAP/Col specimens were implanted. After feeding for 1 day, 4 weeks, or 8 weeks, the rats were sacrificed (n=6). Micro-computed tomography (CT) revealed that at 4 and 8 weeks the defect zones implanted with Col had similar mean opacity values of around 105, compared to that of 70 after 1 day (p<0.05); whereas at 4 weeks those implanted with n-HAP /Col had a much larger mean opacity value of 149, compared to those of 109 at 1 day (p<0.05) and 123 at 8 weeks. Histological observations of the rat cranial defect zones implanted with n-HAP/Col for 8 weeks revealed that n-HAP/Col was completely eliminated, and new bone was partially formed. Taken together, it was considered that n-HAP/Col was osteo-conductive, most effective at 4 weeks while newly formed bone slightly decreased at 8 weeks. Withal limited experimental results, it can be concluded that n-HAP/Col could be used as new osteo-conductive bone substitute material. For better osteo-regeneration at cranial defects over 4 weeks, it was recommended to add growth factors and stem cells to n-HAP/Col in future studies.

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Diamond points are used to cut or grind teeth and prostheses in clinical practice. The embryotoxicity of scattered abrasive diamond grains was investigated in patients and practitioners by the Embryonic Stem Cell Test (EST) method. The risks of embryotoxicity should be considered in patients, practitioners, and pregnant and possibly pregnant women. Commercial diamond particles and diamond particles detached by grinding a diamond point were used. Commercial diamond particles slightly lowered ID50 and IC50 values. Diamond particles detached from a diamond point markedly lowered ID50 and IC50 values. These results may be explained by the contaminating plating components of diamond points. In both experiments, ID50 values were higher than IC50 values, demonstrating the low-level effects of diamond particles on ES-D3 cell differentiation.

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Bone mass growth (bone augmentation) is desirable to improve occlusal function in jaws with a decrease in bone mass. Therefore, scaffold with sufficient mechanical strength to secure space for new bone formation is needed. Since coral is a porous scaffold with mechanical strength, we tried a new method for bone augmentation using it as the scaffold. Materials and Methods: Coral disks were implanted under periosteum on the surface of rat skull. Twelve months after the implant procedure, calcein and alizarin red were administered and three days later the skull with the implanted portion was removed and the specimen was observed with a light microscope and confocal laser scanning microscope (CLSM). Results: At twelve months postoperatively, the implanted coral disks remained, while the bone augmentation was observed together with new bone formation including many osteocytes in the inner cavities of the coral disk. There were few inflammatory cells and foreign body giant cells in this area. These findings suggest that though coral disk is weakly bioabsorbable, it is a promising scaffolding material for bone augmentation on the skull.

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