This study evaluated the possibility of the application of bamboo fibers to cold-curing resin. Specimens reinforced by Oo bamboo fibers (P. aurea f. takemural) were fabricated and immersed in distilled water for 1, 7, 30, 90, and 180 days. After immersion, the specimens were tested by the 3-point bending test to measure flexural strengths and rigidity, and the amounts of leached monomer and water sorption were measured. As a result of the test and the measurement, bamboo fibers could reinforce resin, with the reinforcement effect being maintained for 180 days; however, there were increased amounts of leached monomer and water sorption. Clinically, profitable points were identified, but the improvement points were identified also.

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A three-dimensional finite element method was applied to calculate elastic stress distributions of a castable ceramic crown on an upper first premolar. Acting a uniform pressure on the cusp, tensile stresses were produced near the central groove and at the boundary between the crown and abutment tooth. When the angle of the groove, α, the radius of the groove bottom, γ, and the thickness of the crown, t, are small, the tensile stress at the groove becomes large and the groove may be attributed to the fracture of the crown. In crowns having large values of α, γ and t, maximum tensile stress is produced at the crown-tooth boundary. But the magnitude of this stress is very small in comparison with the tensile strength of a castable ceramic. In order to prevent the fracture of the crown, groove angle α, groove radius γ and crown thickness t should be increased as much as possible.

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The purpose of the present study was to develop a screw-incorporated orthodontic bracket to reduce the pain experienced by the patient at debonding and to examine the physical mechanism of its debonding. Debonding is to detach the bonded bracket from the tooth surface when the tip of a mini-screw installed in the bracket base comes out toward the tooth surface by being rotated. This leads to a reduced impact-giving debonding method without the use of debonding pliers. Bond strengths 24 hours after bonding and after 2,000 and 20,000 thermal cycles were examined using a tensile bond strength test, which revealed that the screw bracket has a clinically sufficient bond strength. Light microscopic observation revealed that the detached surface of the bond did not have a uniform topography. The tip of the mini-screw generated a load of 9.11 N on the tooth surface and the mean maximum torque of the mini-screw was 1.89 N・cm.

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This study investigated the optimal conditions of electrodeposition with 4-META on type 4 gold alloy. Shear bond strength between light-curing prosthetic resin and type 4 gold alloy electrodeposited under the conditions of various concentrations of 4-MET and current intensities was measured. The values of bond strength with electrodeposition were significantly larger than those of bond strength without electrodeposition. The largest value of bond strength was 14.6MPa, and its condition of electrodeposition was a 20% concentration of 4-MET, with a 100mA/cm² current intensity (referred to as 20%-100mA/cm²). There were no significant differences in the values of bonding strength under condition of electrodeposition among 20%-100mA/cm², 10%-100mA/cm² and 20%-50mA/cm². Test results indicated that electrodeposition with 4-META increased values of bonding strength between light-curing prosthetic resin and type 4 gold alloy, and the optimal conditions were 20%-100mA/cm², 10%-100mA/cm² and 20%-50mA/cm².

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This study examined the effect of water on the mechanical strengths of temporary cements. Commercially available temporary cements (polycarboxylate cement, paste-mix type cement with and without eugenol and powder-liquid type zinc oxide-eugenol cement, two products of each type) were used. An hour after the start of mixing, a cement specimen was kept in either deionized water, a moist atmosphere, or air at 37℃, for up to 672 hours. The compressive strength and diametral tensile strength of each cement were determined. Polycarboxylate cements kept in air were significantly stronger with time than those in other conditions. Changes in strength of the eugenol-containing cements varied among the products tested. Paste-mix cement without eugenol did not show significant changes in strength with time in all the conditions tested. Difference in the dispensing type of cement, such as powder-liquid or paste-mix, is a factor affecting the sensitivity of cement to water.

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We measured the mechanical properties and thicknesses of the castings reaction layers of three experimental titanium alloys (Ti-9.4Ag-9.2Cu alloy, Ti-14.2Ag-9.6Zr alloy and Ti-14.3Ag-9.7Cr alloy) produced by levitation melting. Tensile strength, elongation and Vickers hardness were measured. As a result, the tensile strength of the Ti-9.4Ag-9.2Cu alloy was 781MPa. The Ti-14.2Ag-9.6Zr alloy, which was mixed with silver and zirconium, showed an elongation of 14.4% and Vickers hardness of Hv 257. The thickness of the castings reaction layer of each experimental titanium alloy casting was lower when compared with pure titanium castings.

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In all-in-one adhesive systems, because of the low etching ability of acidic monomers, the thick smear layer may affect the bonding efficacy of the adhesive systems. In this study, the effect of grinding surface on microtensile bond strength to dentin of 2 all-in-one adhesive systems, i Bond and G-BOND, was investigated. Dentin surface was ground with three different courses of SiC papers. In the results, the etching ability of the adhesive systems was weak strong and the grinding surface had little effect on the bond strength to dentin. When the rougher surface was bonded, numerous voids were exposed on the fractured surfaces of the adhesive layer. It was suggested that the grinding surface had an effect of the bond strength to dentin in i Bond, although structural faults were formed at the bonding interface when the rougher surface was produced.

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This study examined the changes in shear strength of glass ionomer cements for luting with time. Four commercially available glass ionomer cements for luting with different setting modes (conventional type and resin-modified type) were used. Disk specimens (10mm dia., 1.0mm thick) were prepared and immersed in deionized water at 37℃ for 24 hours, 1, 4 or 8 weeks. The shear strengths of cements were determined using a punch tool. The Weibull moduli of strength data for the cements were also obtained. Conventional glass ionomer cements increased their strengths up to 4 weeks. However, resin-modified glass ionomer cements did not exhibit a specific trend concerning changes in strength. The resin-modified glass ionomer cements showed a greater strength and greater increase in weight than conventional cements. Weibull analysis suggested that the resin-modified glass ionomer cements possessed greater fracture resistance in shear stress mode compared to the conventional cements.

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Density, polymerization shrinkage, filler content, constituent elements of filler and thermal expansion of ten composite resins (A3 enamel and dentin pastes) for crown and bridge were measured. Density of composite pastes was 1.493-2.528g/cm³, and that of set composites was 1.588-2.561g/cm³. Polymerization shrinkage of composites was 1.17-5.98 vol%. Inorganic filler content was 44.9-88.3wt%. Si or Al was the main component element of inorganic filler, and Ba, La, Sr, Zr and Zn were added as X-ray opaque materials. Thermal expansion was 16.8-96.4×10^-6/℃ (30-80℃). With an increase in inorganic filler, polymerization shrinkage and thermal expansion decreased.

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