Quantitative assessments of cytotoxic effects on the cell cycle were analyzed.Several sets of DNA histograms including transient responses of HeLa cells exposed to 10μM CdCl₂ and of LSC cells exposed to 2, 000 or 3, 200μg/ml MMA by Flow Cytometry were put into a mathematical model using a continuous linear system.Changes in the rate of progression caused by the cytotoxic effects and some artifacts were explained as the sum of partial differences and were estimated from the parameters of the System Dynamics Model using the transient responses on the tests.In HeLa cells, CdCl₂ elongated progression of the S phase by 20% and the G₂ phase by 25% compared to the control.In LSC cells, MMA elongated progression of the S phase by 50% and the G₂+M phases by 80〜83%.After the mitotic phase, about half of the cells showed a decrease in the relative amount of DNA compared to that of the normal G₁ phase.

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Polyblend powders, which were mechanically blended into polymethyl-methacrylate(PMMA), were produced using two thermoplastic elastomers(syndiotactic 1, 2polybutadiene(BR)and stylene-isoprene-stylene(SIS)).Using there powders, conventional polymerization was carried out.For ten materials obtained according to the conventional curing technique, dynamic viscoelastic properties(G'and η'), coefficient of thermal expansion, water absorption, residual monomer(MMA)and impact strength were examined.G'(dynamic shear modulus)decreased 26% compared with that of PMMA in a temperature range from room temperature(23±1.0℃)to 100℃.η'(coefficient of dynamic viscosity)also decreased and its rate of decrease was 30.8%.Although the amounts of thermal expansion of both materials(blended with BR and SIS)were less than that of PMMA in air, there were no significant difference between polyblends and PMMA.On the other hand, the amounts of thermal expansion and residual monomer increased gradually with the increase of elastomer.Furthermore, bending strength and strain energy were also increased, and impact strength of their materials was markedly improved.

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To develop a more effective primer, it is important to understand how the primer enhances the adhesiveness of resin to etched-dentin.In this study, the N-methacryloyl-ω-amino acid(NMωA)was designed for dentin primer.The effects of the number of methylene in the NMωA primer on the strength of the interaction between NMωA and dentinal collagen, and on the bond strength of resin to etched-dentin primed with NMωA were investigated.The amide and carboxylic acid in the NMωA molecule interacted with dentinal collagen.The interaction became stronger by increasing the methylene chain length in the NMωA molecule.The bond strength of resin to etched-dentin primed with NMωA increased, reflecting the strength of the interaction.The bond strength of resin to etched-dentin primed with NMωA strongly depended on the strength of the interaction between NMωA and dentinal collagen.

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Recently, biocompatibility has become a great concern in biomaterials, and demands for dental gold alloys with better biocompatibility have consequently increased.Since titanium has a small solid-solubility in gold, a new type of gold alloy which combines good biocompatibility, color tone, and mechanical properties is expected to be developed by adding a small quantity of titanium to gold.In this paper, gold-titanium alloys with a titanium content of 0.5〜2.0mass% were created and their heat-treating conditions, mechanical properties, structures, and colors were examined to explore the feasibility of applying these metals to dental casting.As a result, the optimal condition for solutionizing was 1, 000℃ for 10 minutes, and that for age-hardening was 600℃ for 10 minutes.The optimal amount of titanium was 1.0〜1.8%.As the mechanical properties of gold-titanium alloys ranged from soft to extra hard depending on titanium content and heat-treating conditions, gold-titanium alloys may be suitable for a wide range of dental application.

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