[in Japanese]

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Ideal esthetic restorative materials should have similar properties of light reflection, scattering, fluorescence and opalescence to those of natural teeth. Instrumental technologies that quantify color and color-difference are widely used. However, parameters for the size of perceptible and acceptable color-differences in esthetic restorations are varied; therefore new color-difference formulas were introduced. Metamerism was proposed as the largest single cause of industrial color matching and acceptance problems. In addition to the color and color coordinates, enhanced opalescence and fluorescence may result in color-reactive material that looks natural and esthetic in any light and reacts to light in the same manner as the natural dentition. Opalescence was reported as a contributor to the vitality of a restoration, and was included as a parameter for the dental color determination. The following topics were studied to evaluate varied optical properties of esthetic dental materials.The correlation between color-difference values calculated with delta E*ab (CIELAB) and delta E00 (CIEDE2000) formulas was measured after polymerization and thermocycling of dental resin composites, and the order and correlation of influencing variables on the discrepancy of color-difference values calculated by two formulas (delta E00-delta E*ab) were determined. As a result, significant changes in weighing functions and parametric functions were involved during polymerization and thermocycling of resin composites. Since delta E00 formula was proved to be more matched to observer responses, the new formula should be considered for evaluating color-difference of dental substances. Metameric color changes between resin composites and dentin was determined and the changes in lightness, chroma, hue and hue angle under the three standard illuminants (D65, A and F2) were evaluated. As a result, metameric effect between dentin and resin composites varied depending on the shade of dentin and resin composite, and on the color parameters of lightness, chroma, hue and hue angle. Therefore these factors should be considered in color matching. Fluorescence of resin composites was measured with a color measuring spectrophotometer. From the spectral reflectance values, the difference in reflectance by the inclusion and exclusion of UV component of the illuminant was calculated. As a result, some commercial resin composites showed fluorescence, and others did not. Opalescence of resin composites was measured with a color measuring spectrophotometer. Colors measured in the reflectance and transmittance modes were compared, and a parameter that could predict the opalescence of resin composites was determined. As a result, opalescence varied by the material and shade of the resin composites, and contributed to the masking of background color along with translucency parameter.

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Calcium phosphates have been subjects of the intensive research in the last decades. There are two types of calcium phosphate materials: Bioactive and bioresorbable. For example, sintered hydroxyapatite has been described as bioactive but nonresorbable. Biphasic calcium phosphate, calcium phosphate cements that form precipitated hydroxyapatite or other calcium phosphate phases, certain calcium phosphate coatings, bioglass are bioresorbable. Bioactive materials are biocompatible, and are directly bonded to bone. Bioresorbable materials are biocompatible and are resorbed by osteoclast, leading to new bone formation. A calcium phosphate cement consisting of tetracalcium phosphate and dicalcium phosphate anhydrous or dicalcium phosphate dihydrate reacts with water to harden and form nano-HA crystals as product, as a result it is biocompatible and bioresorbable. Therefore, these calcium phosphate biomaterials are useful in medical and dental applications. These include: an endodontic filling material, an implant material for periodontal bone defects and alveolar ridge augmentation, a coating material to stabilize metal implants. The presentations given in this symposium will highlight some of the most important advances in the use of electrochemical deposition or chemical precipitation methods to form calcium phosphate coatings on metal surfaces and in calcium phosphate cements.

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Commercial orthopedic and dental implants coated by plasma-sprayed HA combines the strength of titanium (Ti) or Ti alloy and the bioactivity of HA. However, the plasma-spray coating method has the following disadvantages: coating obtained has inhomogenous composition (e.g., variable concentrations of HA and amorphous calcium phosphate, ACP, hence variable HA/ACP ratios from between the outer and inner layers of the coating leading to unpredictable biodegradation; does not permit coating of implant with complex geometry; and high temperature does not allow incorporation of bioactive molecules. The purpose of this study was to deposit octacalcium phosphate (OCP) and different types of apatites (calcium deficient apatites, AP; fluoride-substituted (FAP) and carbonate-substituted (CHA) apatites on Ti (Ti6Al4V) substrates using pulse-modulated electrochemical deposition (ECD) method. Studies showed that using pulse modulated ECD, desired homogeneous coating composition (OCP, AP, FAP, CHA) and thickness (10m or thicker) can be obtained at low temperature (25, 37 or 60 oC) by appropriate adjustments of pH, temperature and electrolyte composition.

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Due to their good physical (self-hardening, moldable, strength, etc.) and in vivo (biocompatible, osteoconductive, resorbable) properties, calcium phosphate cements (CPCs) and related materials have the potential to replace allografts and eventually autografts for bone defects repair. Currently, several CPCs have been approved for clinical use throughout the world. However, at present time their uses remain largely limited to craniofacial and selected non-load bearing orthopedic applications. Efforts are being made to build into CPC materials those attributes that are of critical importance for various clinical applications. These include (1) a wide range of hardening times and with high washout resistance, (2) a range of in vivo resorption rates, (3) elastomeric qualities that can reduce implant fracture or accommodate inherent micro movements within the bone tissues, (4) macropores of various shapes and pore volumes, (5) significantly greater flexural strengths by fiber reinforcement, (5) inclusion of osteoinductive factors, and (6) premixed cement pastes that are stable in the package and hardens rapidly after delivery to defect site. It is anticipated that further research will lead development of CPC materials with properties that are uniquely suitable for specific clinical applications.

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[in Japanese]

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[in Japanese]

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It had reported that Hydroxyapatite (HA) was able to be electrically polarized and that the electrical polarization was found to enhance new bone formation. Osteoblast adhesion was required for reconstruction in the vicinities of implantable biomatelials surfaces. In the present study, Western blotting was examined to test the hypothesis that the electrically polarized hydroxyapatite adsorb more fibronectin and vitronectin from serum than the non-polarised hydroxyapatite.

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Yttrium-oxide-partially-stabilized zirconia has been used in dentistry. Whereas, to further improve its mechanical strength, the zirconia/alumina nano-composite stabilized with cerium oxide was developed in Japan several years ago. In the present study, mechanical strength was determined to evaluate the possibility of application to all ceramic crowns.

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[in Japanese]

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In recent years three-dimensional diagnoses became actively done, and MR image is often used especially in diagnosing the soft tissue and the organization properties. However, metal artifact caused by dental prostheses often disturbs the image.In the present study, we examined the phenomena and origin of metal artifacts, and discussed on the reduction of them using compact MRI ( NEOMAX Ltd.)

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Flapless implant surgery has recently been notable as a less inversion procedure in dentistry. But, this procedure involves more risks than usual procedures.In this study, to realize more safe and quick implant surgery, surgical stent and a provisional restoration for immediate loading were designed by CAD using haptic device, and fabricated by RP (rapid prototyping).We applied fabricated stent and provisional restoration to patients.

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Tooth extraction is one of the constitutive subjects for dental clinical education. However, in the practical education, very few students can experience the tooth extraction. In order to cover this situation, computer simulation will be effective. In the present study, we will report on a simulation of tooth extraction by operating 3D-CT image of a patient using haptic device.

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The simulation of the laser welding process of a titanium board was carried out using the finite element method. Consequently, in isotropic heat conduction, it did not generate but the key hole type dissolution generated the key hole type dissolution only in different direction heat conduction. From these results, when metal was heated more than bolling point , it became clear that a key hole occurs.

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[in Japanese]

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Titanium and its alloys are well known to decrease the corrosion resistance in the saline solution containing fluoride. We recently reported that Ti-20mass% Cr had good corrosion resistance in the saline solution containing fluoride. In this study, we made the Ti-Cr casting alloy containing 5, 10, 15 or 20mass% Cr content, and evaluated the electrochemical corrosion behavior of them in saline solution and saline solution containing fluoride

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[in Japanese]

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Commercial pure titanium (Ti) was annealed in an ambient air, and formed oxide films on its surface. A part of the specimens were removed the oxide films by abrasion. The both of the specimens were immersed in APF, which was mixed solution of 2.0% NaF and 1.7% H3PO4. The effect of surface oxide films, which were formed by annealing, on degradation of titanium in APF was measured by thermal desorption spectrometer. Amounts of hydrogen in the specimens could detect as a function of heating temperature. The different detection curves were obtained between the specimens with and without the oxide films by annealing. It was concluded that the s

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[in Japanese]

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[in Japanese]

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An epicutaneous patch testing has been conventionally used to demonstrate hypersensitivity reaction to metals. In the present study, we evaluated the stability of metal ions in solution used for patch testing. It was demonstrated that palladium ions are hydrolysed to produce hydroxide with lowering the pH of the solution from 7 to 2. These results suggest that the stabolity of metal ions ant its relation to pH of the test solution used for patch testing is one of the most important factor to improve reliability of an epicutaneous patch testing.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The purpose of this study is to developed a biofunctional implantmaterials. We prepared BMP-resin complexes and evaluated these materials in vivo. Samples were examined by soft X-ray and histological observation at 4weeks after implantation.

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[in Japanese]

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We evaluated m-RNA gene-expression of RAW264 cells exposed to high dose of Ni²⁺ ion (500micro-mol/L) by DNA microarray. After 1 day culture, 111 genes were significantly expressed. Characteristically, SOD1, metallothionein 2 and 70kDa heat shock protein genes were up-regulated, while cyclin A1 gene was down-regulated. SOD activity was also dose-dependently increased by Ni²⁺ ion.

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[in Japanese]

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The aim was to characterize the structure of calcified materials removed the oral cavity by EPMA and XRD. The samples, spatter-coated with platinum or carbon, were observed by a scanning electron microscope (S-4500: Hitachi), an energy-dispersive X-ray spectroscope (EMAX-650: Hitachi) and XRD(RINT-2500:Rigaku). The calcified tissue was found hydroxyapatite with high density.

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[in Japanese]

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[in Japanese]

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In order to propose adhesion theory in newly-designed dentine adhesive materials, we measured the dynamic property of hybrid layer using nano-indentation technique. And then the propertiesand the size of plastic deformation were discussed by means oftheoretical analysis of plastic deformation of hybrid layer. In addition,adhesive strength and fracture strength in micro- tensile bond test were discussed theoretically. We propose adhesion theory in new generation of dental adhesive materials.

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The aim of this study was to characterize the adhesive performance of three functional monomers, 10-MDP, 4-MET, and phenyl-P, with hydroxyapatite, and to determine the hydrolytic stability of 3 self-etch adhesives, Clearfil MegaBond (CMB), Unifil Bond (UFB) or Clearfil Liner Bond II (LBII). Among these monomers, 10-MDP appeared not only to interact most intensively with hydroxyapatite; its bond with calcium appeared also most hydrolytically stable. Even after 100000 cycles, the 10-MDP-based adhesive (CMB) revealed an micro-TBS of 35.3 MPa, which was not significantly different from the control micro-TBS (40.8 MPa). The 4-MET-based adhesive (UFB) showed statistically the same micro-TBS as the control (37.9 MPa) up to 50000 cycles, but after 100000 cycles its micro-TBS was significantly lower (22.5 MPa). For the phenyl-P-based adhesive (LBII), the micro-TBS decreased significantly after 30000 cycles from the control value (44.7 MPa) towards 23.2 MPa after 100000 cycles.

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[in Japanese]

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[in Japanese]

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Commercial pure titanium wires were annealed at 600 and 800C for 2 hours in an ambient air, and formed oxide films on these surfaces. A part of the specimens annealed were removed the surface films after annealing. The specimens were immersed in an acidulated phosphate fluoride (APF) solution. The mass change and mechanical strength were measured for both of the specimens with and without oxide films, which were formed by annealing. The degradation of each specimen was confirmed by SEM observation. Effects of the oxide films on protection against corrosion of titanium by fluoride ions were discussed. It was concluded that the oxide films on titanium might be protected the degradation of titanium in the APF solution.

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We reported previously that the etching in concentrated acid had great effects on the apatite formation ability of the alkaline treated titanium. In the present study, the effect on the apatite formation using an alternate soaking process was evaluated on this acid/alkaline treated titanium.

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[in Japanese]

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The biological properties of a titanium (Ti) implant depend on its surface oxide film. The aims of the present study were to increase the specific surface oxide area on Ti using a porous structure, and study the relationship between the amounts of apatite coating in simulated body fluid (SBF) and the actual surface area on titanium powders. The amounts of precipitates through the compacts, which had been sintered of the powders with 110 micon meter diameter, were compared with those of the Ti plate. It was confirmed that the amounts of precipitates through the compacts were more than one hundred times higher than those on the Ti plates. It was concluded that the Ti porous compacts extract the surface property effectively.

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[in Japanese]

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[in Japanese]

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