We reviewed the changes in metal structure during fusion and solidification and the distribution of elements using Ag-Pd-Cu-Au alloy, two alloys for metal-bond porcelain (KIK-H II, Degubond-J2) and type III gold alloy. We came to the following conclusions: 1. In the early stage of fusion, the dental-alloy generates crystals with in a minute part of the solid-phase. After that, the crystals dissolve in the liquid-phase and disappear. 2. In the case of solidification, the organization structure in the liquid-phase grows steadily and is maintained even if it enters a solid-phase point. 3. When the cooling rate in the case of solidification is slow, extreme demixing of ingredients with a low melting point, like Sn, occurs. To create a better casting body, precise control of the cooling rate is important.

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The aim of this study was to obtain stable adhesive durability of facing resins to dental metal. The effect of differences in the coefficient of thermal expansion between facing resins and dental metals on adhesive durability was examined. Ag-Pd-Au alloy (AgPd) was treated with primer or electrodeposition with 4-MET and bonded with Estenia (ES), having an approximate value of coefficient of thermal expansion compared with that of AgPd. In the other case, AgPd was bonded with Gradia (GR), having a larger value of coefficient of thermal expansion in comparison with AgPd. Following that, shear bond strength was measured after the thermal cycle test and the adhesive durability was estimated. The adhesive durability of ES was found to be superior to that of GR and both the shear bond strength and adhesive durability after treatment by electrodeposition with 4-MET were superior to those after primer treatment.

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New dental gold alloys were prepared on the basis of the gold alloy 80wt% Au-20wt% Cu by the additions of 1wt%, 2wt%, and 3wt% cobalt. The properties of Vickers hardness, tensile strength, elongation, SEM fractographs, metallography, XRD and corrosion resistance were investigated in comparison with the commercial dental gold alloy of ADA standard Type IV for both after-solution treatment and age-hardening treatment. After age-hardening treatment, the mechanical properties were greatly improved by the addition of Co and become nearly equivalent to Type IV in 2wt% Co and 3wt% Co alloys. ICP analysis after immersion in simulated body fluid showed that the dissolution level of Cu and Co was about the same as commercial gold and Co-Cr alloys. These results indicate that Au-Cu-Co dental alloys have properties equivalent to Type IV gold alloys.

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The objective of the study was to investigate adsorption of the adhesive protein fibrinogen on plates of gold and titanium as a first step in the analysis of reactions at the interface between tissues and dental alloys. For the adsorption test, each gold and titanium plate was immersed in fibrinogen solutions at varying concentrations, and maintained at 37℃ for 1, 3 and 5 days. The amount of adsorbed fibrinogen as a function of the fibrinogen concentration and immersion conditions was analyzed quantitatively using a biochemical method. Surfaces of gold and titanium, after, performing adsorption and desorption tests, were observed by means of an atomic force microscope under aqueous conditions. The results showed that adsorption of fibrinogen was weak on gold but relatively strong on titanium. In conclusion, fibrinogen attaches mainly to gold by physical adsorption, but to titanium by chemical adsorption.

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Sandblast-treated titanium (Ti) and 12% Au-Ag-Pd (12Au) alloys underwent observation by laser microscopy and elemental measurement by an EPMA. The whole surface of the specimen was respectively treated with a pencil type sandblaster, glass beads, alumina and carborundum for 10, 30, and 90 seconds. Glass bead-treated Ti and 12Au surfaces showed roundish irregularities. Alumina- and carborundum-treated surfaces showed sharp irregularities. Carborundum showed the greatest elimination depth for 30 seconds, and alumina showed the greatest elimination depth for 90 seconds. Both elimination depths were greater with the extension of processing time. Surface roughness (Ra) became lower for glass beads and greater for alumina and carborundum, compared with an untreated surface. Mapping images showed the constituent elements of glass beads, alumina and carborundum powder on respective treated surfaces.

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To improve the toughness of polycarboxylate cement Calron SmFP, the mechanical properties of the cement containing Alborex® whisker composed of alumino-borate were estimated. As a result, the diametral tensile strength of the cement with whisker was three times stronger than that of the whisker free cement, and the compressive strength increased. The addition of particle fillers with the same composition did not improve the properties. Also, the diametral tensile strengths of Fuji Ionomer TYPE I and HY-BOND CARBO cement with the whisker were two times stronger, respectively, than whisker free cement.

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This study examined the effect of light intensities on the shear bond strengths of adhesive resin cements to ceramic blocks. Two commercially available dual-cured adhesive resin cements and a CAD/CAM ceramic plate were used. Each adhesive resin cement bonded to the ceramic plate at two different thicknesses (1 or 3mm) using light curing unit at two different light intensities (300 or 800mW/cm²). Light was irradiated through the ceramic plate to cure the cement. The shear bond strengths of cements to ceramics were measured at 5, 10, 30, 60 minutes or 24 hours after the start of mixing using the universal testing machine. The shear bond strength of cements to ceramics at 800mW/cm² was significantly greater than 300mW/cm² for 5 minutes (p＜0.05). Shear bond strength of cements to ceramics at 1mm was significantly greater than at 3mm for 5 minutes except for P, with B3 shade at 300mW/cm² (p＜0.05). Light intensity could be a factor affecting the bond strength of dual-cured adhesive resin cements to ceramic at the initial setting stage of resin cements.

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