This study examined the effects of air contact and air blowing on residual volatile compounds contents of resin before and after light polymerization. Five experimental resins (Bis-GMA, TEGDMA, and HEMA-based resins) and five adhesive resin systems were examined in this study. The resins were prepared with different methods (with and without air contact or air blowing) to simulate the clinical conditions of adhesive application. The contents of the residual volatile compound in the resins were determined by measuring weight change using a moisture analyzer. The solvents (acetone, ethanol, and water) were easily evaporated under air contact. Although air blowing effectively removed the volatile contents of acetone, ethanol and water from resins, high amounts of volatile compounds remained in HEMA-based resins.
Air blowing removes the volatile compounds (acetone, ethanol or water) from adhesives to different degrees; however, an inverse result may occur in the case of HEMA.

View full abstract

Human mesenchymal stem cells (hMSCs) were cultured in a chondrogenic differentiaton medium on a single multichannel nanopillar sheet with varying morphological parameters such as pillar diameter, pillar diameter to pitch ratio, and ditch width which limits the continuous pillar area, etc. The hMSCs were able to form spheroids on every type of nanopillar surface and their diameters were dependent on the parameters. Diameters of hMSC spheroids had a maximum value at a pillar diameter of 5 mm when the ratio of pillar diameter to pitch was fixed to 1/2 and decreased with increasing ditch width. These phenomena might be explained by the adhering area and migration speed of the hMSCs on the pillar surface.

View full abstract

To generate mature bone tissue in vitro, many types of cells in rabbit bone marrow aspirate were cultured within a rotating wall vessel (RWV) bioreactor. Bone marrow aspirate contains not only mesenchymal stem cells (MSCs) but also hematopoietic stem cells (HSCs), osteoblasts, osteocytes, osteoclasts, etc. Non-adherent cells in bone marrow aspirate were co-cultured with MSCs and MSC-derived endothelial cells under rotating condition with an RWV bioreactor. The engineered tissue was analyzed histochemically, and high-density tissue, a pre-bone-like structure containing osteoclast-like cells and thick vascular-like structures (approximately 50μm in diameter) were observed. Moreover, MSC-derived osteoblasts were co-cultured with these cells, and osteogenesis of cultured tissue was accelerated. Many types of cells and growth factors can repeatedly interact with each other in a rotating culture with an RWV bioreactor. These conditions could provide an excellent controlled environment for constructing bone tissue in vitro.

View full abstract

A nano-filled resin composite is strengthened by the nano-sized filler particles. Ion release and buffering capacity of functional filler-containing fissure sealants (FSs) were studied. Three resin sealants (S-PRG filler-containing FS: BeautiSealant (BS), DELTON (DE), Teethmate F1-2.0 (TM) and a glass-ionomer cement sealant; Fuji III LC (III LC) were prepared. Disks of 13 mm in diameter and 1 mm in thickness (n=4) were incubated for 24 hours into 5 mL lactic acid of pH 4.0 at 37°C. ICP ion analysis revealed that BS released large amounts of Si, Sr, Al, B and Na. III LC released large amounts of Si, Sr, Al and Na. DE released large amount of Na. TM released the smallest amounts of ions. Fluoride measured by an ion meter showed a higher value in III LC than in BS, DE or TM. The filler-containing sealants showed a substantial increase from the initial pH 4.0 of lactic acid toward neutral pH, demonstrating buffering capacity of sealants. Such changes were accompanied by modest release of alkaline ions. This was outstanding in BS. S-PRG technology enables the formation of a stable glass-ionomer phase on the surface of multi-functional glass particles, maintaining their basic properties.

View full abstract

The formaldehyde reduction activity of fired scallop-shell powder was investigated by means of ab initio and density functional theory calculations. The two active components of fired scallop-shell powder are considered to be calcium oxide (CaO) and calcium hydroxide (Ca(OH)₂). In this study, finite-sized cluster models of these compounds were made and the interaction between each of them and formaldehyde (HCHO) was analyzed theoretically. Comparing the adsorption states of HCHO contained in the two models, one H atom of HCHO in the Ca(OH)₂-HCHO model was found to transfer to the adjacent O atom to form a Ca-OH-C-H-OH five-membered ring structure. This change would lead HCHO to decompose. By contrast, in the case of the CaO-HCHO model, HCHO attaches only through a Ca-O=CH₂-O bridged geometry and does not decompose. This result would indicate why Ca(OH)₂ is effective for HCHO reduction.

View full abstract

We examined the differentiation capacity of mouse embryonic stem (ES) cells cultured on C60 fullerene, as well as cell viability effects, employing a cellular differentiation technique for the embryonic stem cell test (EST). The results demonstrated minor effects on differentiation assay, beating myocardial rate of the dispersed solution was noted in 72% of the control. In addition, there was no influence on cell viability. In this study, the C60 fullerene did not influence the differentiation of ES-D3 cells and "non embryotoxicity". We here investigated C60 fullerene dispersed in a medium. We expected a result of natural dispersion of C60 fullerene into the medium by agitation as possible. This is probably because C60 fullerene did not dispersed. Fullerene particles should be sufficiently dispersed in media. In the future, the biological safety should be comprehensively ex-amined by improving dispersion in medium.

View full abstract

The primary purpose of this study was to analyze the effects of IC₅₀ nickel (Ni) (2+) ions on expressions of seven DNA-damage-recovery genes (Mre11a, Dclre1a, Ddb1, Msh3, Rad51, Ercc1 and Xpa) of mouse macrophage-like cell line RAW264 cultured for 4h and 24h. Quantitative real-time RT-PCR analyses revealed that IC₅₀ Ni (2+) ions significantly down-regulated expressions of these seven genes with time. Additional analyses clarified that IC₅₀ Ni (2+) ions up-regulated expression of two cell-protection genes (Hmox1 and Ier3) and one anti-metal-toxicity gene (MT1) of RAW264 cells with time. Taken together, our data suggested that excessive (i.e. IC₅₀ concentration) Ni (2+) ions overcame intrinsic cell protective mechanisms of RAW264 cells, and inhibited productions of DNA-damage-recovery genes, leading to reduced cell viabilities.

View full abstract

In this study, we succeeded in preparation and characterization of poly(lactic acid)-coated silicon dioxide particles. Poly(lactic acid) was well-known as a biocompatible polymer. The obtained particles indicated excellent cytocompatibility. For determination of the biodistribution, the obtained particles were administered to mice through the tail vein. After administration, the particles were determined in some organs with energy-dispersed X-ray spectrometer. The polymer-coated silicon dioxide particles were observed in the lung, liver, and spleen. In addition, the particles also detected in the thyroid based on inductively coupled plasma - atomic emission spectroscopy. The distribution behaviors were quite different from non-polymer coated inorganic particles.

View full abstract

Tissue stem cells differentiate or dedifferentiate differently from germ cells. Germ cells differentiate to maintain homeostasis of the body or species. ES and iPS cells temporally or automatically differentiate to maintain an in vitro culture environment. Thus, the effects of nanomaterials or agents on ES and iPS cell differentiation can be easily examined. Their effects on tissue stem cell differentiation may also be examined. Additionally, today, their effects on dedifferentiation can be examined with various markers. Furthermore, robust differentiation and dedifferentiation mechanisms will be examined, and the involvement of nanomaterials in carcinogenesis will be elucidated.

View full abstract