Primary cultured cells derived from human pulp tissue were used for examining the cytotoxicity of nine commercial fillng materials used in restoration and root canal procedures. Cell growth was evaluated by photo pattern analysis, cell nuclei counting, and neutral red uptake. L-strain cells were also used for comparison. Primary cultured cells from either the coronary or radicular part of the pulp tissue were less sensitive to the tested materials, than were L-cells. As for sensitivities over time following mixing of the materials, the cytotoxicity of the three restorative materials was immediately moderate but disappeared 24 hours after mixing. The other six root canal filling materials yielded similar moderate to high cytotoxic levels immediately after mixing and the effects continued. The order of cytotoxicity was: Diaket and Calvital (highest); Pulp canal sealer, AH-26, and Canals (high); and then Kloroperka and three restorative materials (moderate). The differences in cellular reactions between primary and strain cells was considered to be due to cell origin, i.e. diploid or heteroploid. The importance of using primary cultured cells from designated target tissues when evaluating various materials in vitro was discussed.

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The retention of crowns cemented on abutment tooth model was examined for three types of luting cements when compressive loads of 2.5 to 10.0kg were repeatedly applied to the occlusal plane.The chamfer type Ni-Cr alloy crown and abutment tooth model were prepared, and their surfaces to be cemented were sandblasted with glass beads.Loads were applied 7, 200 times a day for 1, 3, or 7-day period after cementing.The polycarboxylate and zinc phosphate cements showed higher crown retettions than glass ionomer cements.Although retention strength of glass ionomer cements was significantly increased by storing the cemented specimen in water for 7 days, repeated loading tended to decrease retention.In polycarboxylate cements and one brand of zinc phosphate cement employed, retention strengths were decreased when stored in water over 3 days.However, their highest levels were maintained or even positively impacted by repeated loading for 7 days.

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The wetting action of gallium alloy is a handicap when handling the material.Ethanol mulling after mixing was assayed in an attempt to control wetting action of such mixtures.A mixture of gallium and Ag-Sn-Cu spherical alloy particles was mulled with a small piece of an ethanol-soaked sponge for 10seconds following mixing by an amalgamator.The effect of this mulling on the adherence of the mixture to the capsules, physical properties and microstructures was determined.Mulling with ethanol effectively controlled the wetting action of the mixture, and reduced adherence to the capsules without affecting physical properties.A decreased reaction phase around the alloy particles was observed in the microstructure of the ethanol-mulled specimen.

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Reactions of calcium ions and organic phosphate ester monomers were examined at 60℃ and 80℃ and at various pH. By a modification of the method used for HAp synthesis, calcium acetate was fed into aqueous solution of mechanically stirred mono (methacryloyloxyethyl) acid phosphate. Above a pH of 10, poorly crystallized hydroxyapatite was formed with lower crystallinity than that synthesized with inorganic phosphate as a source of P under the same conditions. This result suggested that phosphate ester and/or decomposed acrylic monomer may inhibit the diffusion of Ca²⁺ and PO₄^3- and the formation of the apatite crystal. On the other hand, the results of X-ray diffraction, chemical analysis, and infrared absorption analysis suggested that crystalline organic calcium phosphate ester was formed below pH10, while in synthesis with inorganic phosphate, hydroxyapatite was formed at pH7.4.

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Deformation of the anterior teeth and palatal regions on upper complete dentures was investigated using the photoelastic coating method and strain gages.In this experiment, an uniform-moment bending load method was employed to simulate the occlusal situation, and the distribution of strain in epoxy resin, stainless swaged and Co-Cr alloy cast dentures were measured and analyzed.The 030-series reflection polariscope is compact and lightweight with its main components consisting of two polarizer/quarter-wave-plate assemblies attached to a common frame.The highest level of strain was seen in the anterior region of the palate and the low strain was observed in other regions.Differences in strain magnitude of the three deutures were not observed with test at the same point.But, when denture base materials with high flexural rigidity and bending strength were used on the palatal region of the denture base, strain was decreased in the anterior and other regions of the palate.Therefore, dentures using those materials could be effectively reinforced.

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Self-setting apatite cement hardens into a mass of single phase apatite when mixed with diluted phosphoric acid. Structurally this mass consists of two types of apatite, i.e. the seed apatite used as a setting accelerator and the matrix apatite formed afterward in the reaction of dicalcium phosphate dihydrate (DCPD) and tetracalcium phosphate (Te-CP). To investigate the dissolution behavior of self-setting apatite cement in detail, two types of ⁴⁵Ca labeled apatite cement were prepared. In one, the seed apatite was labeled with ⁴⁵Ca (⁴⁵Ca-HAp cement) and in the other the matrix apatite was labeled with ⁴⁵Ca through use of ⁴⁵Ca-DCPD (⁴⁵Ca-DCPD cement). Solubility, estimated from the concentration of ⁴⁵Ca released in 1mM of organic acid (e.q. acetic, lactic, or citric acid) with initial pH adjusted to 4.0 at 37℃, was approximately zero for ⁴⁵Ca-HAp cement, whereas the solubility of ⁴⁵Ca-DCPD cement was approximately the same as unlabeled cements used so far. This finding suggests that dissolution of the matrix apatite governs dissolution of the set cement, though comparison of X-ray diffraction patterns and electron micrographs of the seed apatite and apatite in the set cement showed no essential difference in crystallinity and crystal shape. The fact that the matrix apatite was formed by enveloping the seed apatite may account for the preferential dissolution of matrix apatite. In synthetic saliva labeled with ⁴⁵Ca having a degree of supersaturation with respect to apatite comparable to rest saliva, ⁴⁵Ca concentration in solution decreased once the cement pellet was introduced. This finding clearly suggests that the set apatite cement has the ability to remineralize but not dissolve in synthetic saliva even if the degree of supersaturation with respect to apatite is relatively low.

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A light-cured bonding agent consisted of 50wt% BisGMA and 50wt% 2HEMA was prepared in order to investigate the effect of light curing system on the bonding to etched dentin treated with 37wt% phosphoric acid (PA), 10wt% citric acid (CA), 10wt% maleic acid (MA), 10wt% citric acid-3wt% ferric chloride (10-3) and 0.5M EDTA・2Na (EDTA) solutions. The bond strength to dentin treated with 10-3 solution was statistically higher than to dentin treated with the other etchant. The acid-proof dentin layers with about 1〜2μm thickness at the interface between resin and dentin treated with CA, MA, and 10-3 solutions were visible with SEM. The presence of Ca, P, and Br elements in the layers was confirmed by EPMA analysis. The bond strength was greatly dependent upon the physical property of the layer because difference in Knoop hardness of the etched dentin surfaces and the dentin surface after bond testing was greatest when used 10-3 solution.

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In order to understand the interface-phenomena between titanium and biological tissue, the surface film formed on titanium in electrolytic solutions was examined using X-ray photoelectron spectroscopy (XPS). The composition of the surface film on titanium before immersion into solution is close to TiO₂ and that of Ti-6Al-4V is a mixture of TiO₂ and Al₂O₃. These surface films change to a complex phosphate of titanium and calcium containing hydroxyl radicals and hydrates when the specimens are immersed in an electrolytic solution. The compositions of the surface films of titanium and Ti-6Al-4V are almost the same except that the film on Ti-6Al-4V is thicker and contains more hydrates than that on titanium. Vanadium in Ti-6Al-V, and sodium, chlorine, and sulfur in the solution are not responsible for the formation of the films.

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The purpose of the study was to investigate the influence of the isoelectric point and residue of an amino acid on the adsorption of the amino acid by titanium in order to elucidate the adsorption of proteins by titanium.The direction of amino acid adsorbed by a titanium surface in an electrolytic solution was determined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared reflection absorption spectroscopy (FT-IR-RAS). Apparently, the influence of amino acid on the composition and thickness of surface films on titanium is minimal if the film is formed in an electrolytic solution.The pH of the electrolytic solution and the residue of amino acids are responsible for the direction of the amino acid adsorbed by surface film formed on titanium in solution.

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A normalizing method for determining the mode of crack-propagation in a phase or component of a dental amalgam or composite resin was devised.The results calculated using the method were found to be satisfactory when the method was applied to the materials.Furthermore, datails of the mode of crack-propagation in the materials whick cannot be seen using pictures of the cross-section structure of the materials are revealed using the method.

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An investigation was undertaken to evaluate the effect of both photoinitiators (camphorquinone-amine systems) and the adhesion promoting monomer (4-MET) on photopolymerization of bonding liners and their adhesion to dentin. Photopolymerization of bonding liners was measured with differential scanning calorimetry (DSC). The bonding liner containing 2-(dimethylamino) ethyl methacrylate (DMAEMA) as a reducing agent decreased the rate of polymerization in the presence of 4-MET. On the other hand, the bonding liners containing N-phenylglycine (NGP) and N, N-dimethylaniline derivatives as a reducing agent showed good polymerization in the presence of 4-MET. The results of the tensile bond test suggested that bonding liners containing NPG and 4-(dimethylamino) benzoic acid (DMABA), one of the N, N-dimethylaniline derivatives, with or without 4-MET bonded well to dentin treated with EDTA 3-2.NPG and DMABA are recommended not only as reducing agents but also as aids in the diffusion of monomers into the dentin substrate.The relationship between the strength of the bond to dentin and photoirradiation of the bonding liner and composite resin was studied. Elongation of photoirradiation of both the bonding liner and composite resin was effective in impacting the strength of the bond to dentin. Furthermore, sufficient photoirradiation of the bonding liner prior to any filling of composite resin was especially important to obtain high bond strengths. SEM and TEM observations supported good adhesion being achieved by hybrid formations between photocurable bonding liners and dentin.

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A three dimensional shape measurement using a wide area teeth model was constructed using a high precision laser displacement meter, teeth model scanning machine and personal computer. The system employed a Z-directional movement of a laser displacement meter which tracked wide and complicated changes of shape, allowing for the accurate measurement of not only the crown and alveolar crista of the molar, but also maxillary root, the height difference between which extends about 25mm. As for the labialis of the incisors, teeth model was stood on a gonio stage and measured. In the present study, arrange arc and rugged array of incisors were measured. Improvements in the accuracy of measurement were also expected. Higher resolutions were obtained by the measurement at the center of the measurable range of the displacement meter where the laser beam is most focussed. Since the lineality of the measured value varies with the sensitivity coefficient, it the coefficient drifted, values measured in the outer measurable ranges yielded large errors than those in the central positions. The present Z-directional movement enables measurement at the center of the measurable range, yielding smaller errors. The data obtained with the present method of Z-directional movement of a laser displacement meter enables not only the precise measurement of the shape and position of teeth for CAD prosthesis design but also provides basic data for simulation of occlusion by adding the relative positions of the maxilla and mandible to computer models.

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We developed the light cured direct relining material and used it clinically. In this study, a partial change in its components was made to improve both its strength and manipulability with the aim of using it as a denture base material. The physical properties of the new material, bonding to resin teeth, fit, as well as procedure were discussed. As for physical properties, the bending strength of the new material was increased by improving its organic filler, it becoming comparable to that of heat curing resin. The water absorption of the new material was the lowest of compared materials. The bonding strength of this material to resin teeth was increased by treatment with a light cured bonding agent and the fit of the new material to a test model was comparable to that of heat curing resin. Thus, the new material seems to be quite clinically effective as a denture base resin.

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The effect of the eluate from amalgam on glucan symthesis was investigated in this study in order to elucidate the mechanisms by which plaque accumulation is inhibited on amalgam but not on enamel or composite. Glucosyltransferase (GTase) was prepared from a cultured supernatant of Streptococcus mutans B13 by the ammonium sulfate precipitation method. Five commercial amalgams were tested. The eluate from amalgams was prepared by immersing the amalgam discs (10mm dia.×2mm thick.) into distilled water for 2 weeks. A glucan synthesizing system was compounded using GTase (50μl), [¹⁴C]-sucrose (100μl), distilled water, and the eluate (350μl). After 18h incubation at 37℃, the formed water insoluble glucan was collected on glass fiber filters and its radioactivity was counted. Moreover, concentrations of zinc (Zn) and copper (Cu) in the eluates were determined by atomic absorption spectrophotometry. The eluates from Dispersalloy and Fluor alloy, which eluted Zn, were the most inhibitory for glucan synthesis. Sybraloy, which released Cu to a much greater degree than the other amalgams and its eluate showed intermediate antienzymatic activity. The other amalgams, Hi-atomic M and Spherical-D, did not effect GTase at all. The results indicated that various amalgams strongly impact inhibition rates of glucan formation.

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The creep of chemical activated and visible light activated composite resins was studied using a transverse testing instrument. In additon, the water absorption of their materials was measured, and the effect of the moisture on creep behavior was discussed. The water absorption properties of chemically activated composite resin were smaller than those of light activated composites. However, the former's creep strain increased markedly, in comparison with that of light activated resins. This result indicates that the phenomenon may derive from differences in the reaction accelerators of the composites. Increases in filler content reduced creep strain. Furthermore, the setting reaction of both types of resins was seen proceeding over a fairly long period.

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MMA grafted silk fibers were prepared by graft polymerization initiated by TBB, as a collagen model. The loop strength of the fiber was measured to investigate the relationship between grafting and the adhesion of resin to dentin. The loop strength of the grafted fiber decreased with increases in the degree of grafting since the crystal structure of the silk was destroyed by the process. As for adhesion of resin to dehtin by graft polymerization of MMA onto collagen, graft polymerization strongly influences the tensile bond strength of the resin to dentin because of weakening of the collagen.

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The objective of this study was to prepare a new type water soluble bonding agent, methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS), and to investigate the effect of MS on bonding between resins and tooth substrates. MS is cross-linked with Ca²⁺ supplied by hydroxyapatite in a smeared layer on ground enamel and dentin and sticks to their surface. Samples were prepared by bonding an acrylic rod with MMA-TBB resin to ground enamel and dentin coated with an aqueous mixture of FeCl₃ and 10wt% MS. After immersed in water for 24 hrs, the tensile bond strength was measured. The bond strengths to both enamel and dentin were higher than 11MPa and cohesive failure of cured MMA-TBB resin was observed in every case. This suggested that MS could adhere to tooth substrates with a new bonding mechanism different from the previously reported mechanism of the monomer interpenetration and polymerization.

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The objective of this study was to prepare a new type water-soluble bonding agent, methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS), and to investigate the effect of MS on bonding between resins and tooth substrates. MS is cross-linked with Ca²⁺ released from ground enamel and dentin and could be immobilized on their surface. A sample was prepared by bonding an acrylic rod with a BPO･amine catalyzed selfcuring resin to ground enamel and dentin coated with an aqueous mixture of FeCl₃ and 10wt% MS. After immersion in water for 24hrs, the tensile bond strength was measured. The bond strength to both enamel and dentin was only 2MPa and adhesive failure occurred at the interface between cured MS and self-curing resin. This suggested that cured MS could adversely effect the polymerization of self-curing resins. A second treatment of cured MS on the tooth surface with metallic cations was carried out to minimize the amount of free sulfonic acids in the MS disturbing radical formation in self-curing resin. The second treatment improved the bond strength to 6MPa.

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