The purpose of this study was to clarify the properties of functional filler-containing pit and fissure sealants (FS). Seventy-two specimens were prepared and divided into three groups of three resin sealants ( S-PRG filler-containing FS, DELTON and Teethmate F1-2.0) and one glass-ionomer sealant (Fuji III LC). Each of six discs (6 mm in diameter ×3 mm in thickness) was used for 24-h, 4-week and 12-week experiments. Diametral tensile strength (DTS) and ion release were measured. S-PRG FS and Delton showed high values of DTS (23.2 MPa and 23.5 MPa, respectively) after 24 hours of storage. The DTS values of each sealant remained relatively constant. A large amount of fluoride was initially released from the sealants. However, fluoride release did not influence on DTS. S-PRG filler-containing FS released large amounts of strontium, boron and fluoride ions. Filler-containing sealants release large amounts of ions, contributing to antibacterial effects.
Computational analysis for stable conformation of calcium complex of aromatic methacrylate carboxylic acid monomers and the reactivity towards calcium ion were performed by molecular mechanics (MM) and molecular orbital (MO) calculations. Six kinds of carboxylic acid monomers, 4-META, 4-MET, 4-AETA, 4-methacryloxy phthalic acid (4-MPA), 2-(N-methacryloyl amino)terephthalic acid (2-MATPA) and 5-(N-methacryloyl amino)isophthalic acid (5-MAIPA) were studied. The three-dimensional structure with the lowest steric energy of carboxylic acid monomers and carboxylic acid monomer/Ca complexes were obtained by MM calculation. Steric energies of carboxylic acid monomer/Ca complexes were higher than those of carboxylic acid monomers. The energies of highest occupied MO (HOMO) and lowest unoccupied MO (LUMO) were obtained by MO calculations. A energy differences between carboxylic acid monomer/Ca complex and carboxylic acid monomer (ΔE) and energy differences between LUMO of Ca ion and HOMO of carboxylic acid monomers (ΔE') were obtained. A liner correlation was found between ΔE and ΔE'. It is suggested that computational MM and MO calculation will become one of the useful tools for the analysis of chemical substance and the understanding its biological role in nano biomedical field.
There is considerable investigation into the applications of carbon nanotubes because of their valuable properties. In this study, our goal was to develop several carbon nanotube (CNT)-coated substrates through an amide-bonding process. We prepared polycarboxylated multi-walled CNTs via a carboxylation reaction and then CNT derivatives were tethered to amino groups presented on a titanium, gold or glass substrate in the presence of a condensation agent. The obtained substrates were characterized with a Raman microscope, an atomic force microscope (AFM) and a scanning electron microscope (SEM). Raman mapping images indicated that the CNTs existed on the substrate surface homogeneously, and AFM and SEM observation revealed that the CNTs coating the surfaces had a three-dimensional network nanostructure. The CNTs remained on the surface even after ultrasonication treatment in organic solvent. However, they were removed from the substrate surface after soaking in NaOH aqueous solution. This result suggested that the CNTs were tethered to the substrate through amide bonding.
Transparent poly (methyl methacrylate)/organically modified montmorillonite (PMMA/OMMT) nanocomposites were fabricated using a solution intercalation method. OMMT was modified with quaternary alkylammonium ions. The haze values, which are the ratios of diffuse transmittance to total light transmittance via the nanocomposites, gradually increased with an increasing amount of OMMT; however, the deterioration of total light transmittance was maintained within a narrow range. X-ray diffraction patterns showed that a peak regarded as a (001) d-spacing or a second peak corresponding to (002) plane was shifted toward lower 2θ values indicating the penetration of the PMMA polymer chains into the interlayer regions of OMMT. Board-shaped specimens used for the flexural tests were fabricated by compression molding at 230°C. The specimens were sufficiently transparent for their use as esthetic orthodontic wires. The flexural modulus of the PMMA/OMMT nanocomposites increased favorably with an increasing amount of OMMT. It is reasonable to consider that the addition of OMMT to the nanocomposites effectively improves the stiffness of PMMA without seriously deteriorating its flexibility.
Nano and submicron titanium dioxides are widely used as ingredients of sun screen. Thus, its reproductive and developmental toxicities in humans are of concern. We used two kinds of nano titanium dioxides, involving different production methods and surface coatings. The embryotoxicities of these nano titanium dioxides were determined based on inhibitory effects on the cardiomyocyte differentiation of mouse Embryonic Stem cells. As ultrafine titanium dioxide, titanium dioxide (particle diameter, 0.03-0.05 μm) produced by the sintering method (T1) and that (particle diame-ter, 0.01-0.02 μm) produced by the wet method (T2) were used. T2 may cause little developmental toxicity because it has no potent inhibitory effects on cardiomyocyte differentiation. However, T1 should be further investigated.
Coral is a porous material with tubular cavities that could be effectively used as scaffolding for bone augmentation. To investigate the tissue affinity of coral, we examined its biocompatibility and formation of blood capillaries in vitro, and its chemical characteristics. Coral (montipora digitata) deproteinized with NaOH was used. Normal human dermal fibroblasts (NHDF) and human umbilical vein endothelial cells (HUVEC) were co-cultured. The coral and ceramic bone substitute particles were then seeded in the culture medium. After 10 days of co-culture, the cultured cells were stained immunohistochemically with anti-human CD31 antibody, and the state of capillary formation was observed. Cells without these particles were co-cultured as a control. The coral and ceramic bone substitute particles were soaked in calcium containing buffers (pH 6.0, pH 7.0, pH 8.0) and a culture medium for 48 hours, and the calcium density in the buffer and medium were then measured. The calcium density in a solution without these particles was measured as the control group. After 10 days of co-culture, cells consisting of NHDF and HUVEC grew densely around the coral particles. In vitro, the formation of anti-human CD31-positive blood capillaries was seen around coral particles. However, the formation of capillaries was depressed compared with the control group. The density of calcium in the pH 6.0 and pH 7.0 buffer was increased, whereas that of the pH 8.0 and the culture medium was decreased compared with the control group. These findings suggest that the depression of capillary formation in co-cultures with coral particles was caused by a decrease in the calcium density of the culture medium.
We investigated the effects of reagent-grade and nanostructured zinc oxides on cytotoxicity and angiogenesis. Nanostructured zinc oxide was mixed with fetal carf serum and dispersed to simulate in vivo dispersion. Several reports have already been published on nanostructured zinc oxide. However, whether nanostructured zinc oxide is comparable with conventional zinc oxide is unknown. Thus, we investigated their cytotoxicity using a tissue model. In addition, we compared the effects of these zinc oxides on angiogenesis using a commercial angiogenesis model. As a result, nanostructured zinc oxide exhibited cytotoxicity almost comparable with that of reagent-grade zinc oxide. Reagent-grade zinc oxide barely caused angiogenesis at the concentrations used in the experiment. Nanostructured zinc oxide strongly inhibited angiogenesis. Dispersion was altered by serum at the lowest concentration. In the future, the effects of nanolevel dispersion control on cytotoxicity should be further investigated.