In dental nonprecious cast alloys, microstructure of Ni-base cast alloys and the effect of additional elements were discussed in this article, Part 1.As a result, intermetallic compound of NiMn formed between interdendritic regions of Ni-Mn binary alloys and the secondary arm length of dendritite structure distributed in the range of 30 to 50 μm.In case of Ni-Cu-Mn ternary alloy which was substituted by Cu atom in binary alloy, both eutectic αCu-Mn and intermetallic compound NiMn were found between interdendritic regions.When additional elements of Ag, Sn and Al were added to the Ni-Cu-Mn alloys, the formations of eutectic Ag-Cu and intermetallic compounds as Ni₃Sn and Mn₃Sn were observed for the Ni-Cu-Mn alloys which were respectively composing of Ag and Sn atoms.On the contrary, the Ni-Cu-Mn ternary alloys Al atoms constituted single dendrite structure which had intermetallic compound Ni₃Al partly.Namely, it was clarified that the Ni-Cu-Mn alloys which substituted Sn and Al atoms had small-sized dendrite structure with secondary arm length of about 2.5 to 5.0 μm which was less than those of Ni-Mn and Ni-Cu-Mn alloys.

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　The low molecular components were contained in cured composite restorative resin, those materials were influenced to the chemical stabilities and the mechanical properties of cured resin.Therefore, we have been investigated on the extracts from cured composite restorative resins(Clearfil, Silar, Isopast)dipped into MeOH and H₂O by using HPLC(High Performance Liquid Chromatography).
　The results were obtained as follows;
(1) The components were characterized in the extracts from cured composite resins that dipped into MeOH were as follows;
Clearfil:15 kinds, Silar:11 kinds, Isopast:11 kinds Ten kinds in those components were identified, such as TEGDMA, Bis-GMA, UDMA, GMA, DBP, BPO, TDEA, BA, BPA and Bis-GMA intermediate.
(2) The main components in the extracts from cured composite resins that dipped into MeOH were the monomers(TEGDMA, Bis-GMA, UDMA, Bis-GMA intermediate)and a plasticizer(DBP).
(3) Five or eight kinds of the components were charcterized in the extracts from cured composite resins that dipped into H₂O, and the nine kinds in those components were identified.The solubilities of those components into H₂O are probably as follows;
TEGDMA>GMA, TDEA>BA, Bis-GMA intermediate, BPA>Bis-GMA, UDMA, DBP>BPO.

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　The quantification of amalgam carvability has been experimented through the observation of the scratch resistance values obtained by a surface tester.
　The carvability was quantified by three variables:stress frequency, carving stresses and standard deviation of stresses. Then, the depth of carving on the specimen was measured. The influence of the three factors(Hg-alloy ratio, trituration time and condensation pressure)was, furthermore, examined employing a L₂₇(3¹³)table of orthogonal array based on design of experiment. The results were statistically analyzed.
　The periodic change of amalgam carvability was successfully quantified. The different charactaristics of the products employed were revealed. As to the influences of the three factors, amalgam carvability of the products indicated complex dependence upon them.

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　Following the previous reports on silver and tin, the solubility of casted copper was measured by means of an atomic absorption analyzer. Three factors (solution, time and temperature) were analyzed by design of experiment.
　The factors selected were all highly significant.The kind of solution played the most decisive factor:the most dissolution was revealed in the case of 1% lactic acid solution, the highest amount of dissolution was estimated approximately 0.5 g/cm² after 3 months.No significant periodic and thermal effects were observed in the artificial saliva, while the thermal effect at 60℃ was noted in NaCl solution.The significant effects of both factors were revealed in 1% lactic acid solution.

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　The experimental acrylic resins containing 2, 2, 2-trifluoroethyl methacrylate (TFEMA) were prepared and their mechanical properties and physical characteristics were compared with ordinary methyl methacrylate (MMA)-poly(methyl methacrylate) (PMMA) resins. In the cases of TFEMA-MMA copolymers prepared by bulk polymerization, tensile strength and transverse strength were decreased with increasing amount of TFEMA beyond 50wt%. However, this tendency was not significant for dough molding type resins, and the best properties were observed for the resin composed of poly-TFEMA (PTEMA) as a powder and MMA as a powder and MMA as a liquid. The introduction of TFEMA units into resins reduced their Brinell and Knoop hardness numbers above 30wt% of TFEMA content, and the reduction in hardness was smaller for dough molding type resins, compared with resins prepared by bulk polymerization. Water sorption and contact angle depended on the concentration of TFEMA units in cured resins, regardless of their polymerization methods. The water sorption of PTFEMA resin was found to be 0.1 mg/cm², which was about one fifteenth of the value for the control acrylic resin. The results of albumin adsorption onto resin surfaces revealed that the fluorinated dough molding type resin reduced the relative amount of the protein adsorbed, when compared with the control acrylic resin.

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　Recent remarkable progress in the laser technology has induced many potential applications to dentistry.
　In the present study, by noticing on the preferential cavity formation on the carious tooth to the sound ones by laser irradiation, efficient removal of the dental caries was attempted by controlling the irradiation condition of YAG laser. On the sound bovine tooth, cavities with various size were performed, and 10 to 50% increase in the volume was observed on the black stained tooth.
　Meanwhile, on the bovine enamel with artificial primary caries, facility of cavity formation increased markedly and cavity was produced by the weak irradiation which showed no trace on the sound enamel. In the case of bovine dentine, size of cavity on the artificial caries was two times as large as that of sound dentine. Likewisely, apparent difference was obtained in the human teeth both with artificial and natural caries, and for instance, the cavity on the natural carious teeth was 30 times as large as that on the sound one.

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　Abrasion resistance and wettability of dental polymers (polymethyl methacrylate, polysulfone) coated with ultraviolet-curing resin were studied. The polysulfone (PSF-CB) treated with chlorobenzene was inferior to other samples in abrasion resistance. But the abrasion resistance of the PSF-CB could rise remarkably by coating with ultraviolet-curing resin (Perma Link, Unidic). Compared with brushing the samples in dry, brushing them in saline decreased the amount of abrasion. It was found that coating the dental polymer with ultraviolet-curing resin contributes to resisting abrasion, but doesn't contribute appreciably to strengthening hardness. The wettability of polymethyl methacrylate and Perma Link by glycerin and saline was superior to that of polysulfone and Unidic by these liquids.

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