This study investigated the dentin-cement interface for chemical cured and light-cured restorative glass polyalkenoate cements using Cryo-SEM, removing specimen damage under a temperature of -150〜-160℃.Futhermore, after treatment with 3N HCl, the dentin-cement interface was observed under Cryo-SEM.Appliciation of the Cryo-SEM allowed observation of the dentin-cement interface without specimen damage.The cement matrix-impregnated layer was observed in the superficial layer of dentin after treatment with the CA-agent(10% citric acid, 20% calcium chloride)and K-etch(37% phosphoric acid).With the CA-agent, a stable impregnated layer was observed.It seems that the cement matrix impregnated and set into a deeper layer of the dentin.On SEM, the dentin-cement interface of samples treated with 3N HCl clearly revealed the cement-matrix impregnated layer.

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Chitosan is a polysaccaride extracted from crustacea and absorbed in vivo.A bone filling material was compounded of chitosan sol, calcium oxide, magnesium oxide, zinc oxide and β-tri calcium phosphate.This study measured the setting time, compressive strength, pH and also examined the structure of the bone filling material.The results were as follows;Increasing the amount of CaO, MgO and ZnO decreased the setting time.Increasing the amount of ZnO decreased the pH value at fixed contents of CaO(3%)and MgO(1%).Increasing the amount of CaO and MgO increased the pH value.Increasing the amount of ZnO increased the compressive strength.Increasing the amount of MgO decreased the compressive strength.

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Copolymers with pendant spiro ortho ester(SOE)moiety were synthesized by photoinitiated radical polymerization of methyl methacrylate(MMA)and SOE-containing methacrylate(MASOE).These copolymers were white powders with molecular weights ranging from 9890 to 34100 and the copolymer compositions(MASOE/MMA)of 27-75/73-25.From the IR spectra and solubility in organic solvents of the copolymers, it was confiremed that ring-opening reaction of the SOE moiety of the copolymers did not take place.Further, the powder/liquid polymerization(crosslinking)of the copolymers with MMA in the presence of an ionic initiator(BSS)and the properties of polymers which were obtained by the polymerization were studied.The ring-opening of the SOE moiety obviously occurred during polymerization to crosslinked polymers, from th IR spectra changes.These polymers showed similar or slightly smaller polymerization shrinkage and had a slightly decreased hardness, compared with those of poly(methyl methacrylate).

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The effect of cooling shrinkage of impression materials on the reproducibility of stone casts obtained by hydrophilic addition silicone putty/wash impressions was evaluated using a three-dimensional measuring system.Cylindrical stone casts were made at room and oral temperatures during setting with various thickness ratios between the putty and syringe materials.The results demonstrated that the effect of cooling shrinkage of the impression material on the reproducibility of the stone casts was decreased by reducing the thickness of the syringe material.

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The effect of 4-META acetone solution on the permeability of dentin demineralized with phosphoric acid was investigated.4-META/TEGDMA-CQ, NPG resin was bonded to bovine dentin that had been pretreated with 65wt% phosphoric acid and followed by 4-META acetone solution.Higher tensile bond strength was obtained and hybrid formation later was identified when the acetone solution of 4-META was applied to the wet demineralized dentin.However, the strength, SEM and TEM date suggested that bonding to dried demineralized dentin was inferior regardless of whether 4-META acetone solution pretreatment was carried out.Further studies showed that the amount of resin in the hybrid layer was not sufficient and an exposed collagenous layer remained in the deeper portion of the demineralized dentin.

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Effect of aqueous solutions of Phenyl-P and HEMA on bonding to ground dentin was studies.Samples of ground bovine dentin were pretreated with several solutions of various concentrations of Phenyl-P and HEMA.Photocure bonding agent was composed of 0.5% camphorquinone, 0.5% N-phenylglycine and 0 or 5% Phenyl-P in TEGDMA.The following results were obtained.1.Pretreatment with an aqueous mixture of 10% Phenyl-P in 30% HEMA for 5min increased tensile bond strength to 10MPa.However, tensile bond strength was not increased by an pretreatment with aqueous mixture of 5% Phenyl-P in 30% HEMA even for 10min.2.Optimal HEMA concentration was 20 to 40% in 20% Phenyl-P.3.Phenyl-P in TEGDMA photocure bonding agent is not essential for bonding to dentin pretreated with an aqueous mixture of 20% Phenyl-P in 30% HEMA.

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To improve the mechanical properties and conversion of bulk polymers composed of visible light-cured resin using cyclophosphazene monomers, 5 difunctional monomers were synthesized by introducing some combination of methacryloxyphenylisopropylidenphenoxy group(BPhAMA), methacryloxyethoxy group(EMA)and acryloxyethoxy group(EA)substituents into the cyclophosphazene skeleton.The characteristics of these monomers and the properties and conversion of their bulk photopolymers were evaluated.Mechanical properties, especially brittleness, markedly improved in the 1 BPhAMA and 1 EMA substituents as polymerization groups.The polymer obtained by photopolymerization of this monomer seemed to show the highest conversion among the 5monomers 7 days or more after light irradiation.

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This study investigated five kinds of commercially-available reversible hydrocolloid impression materials and ten kinds of dental stones and their compatibility was evaluated by detail reproduction and surface roughness.The following results were obtained:Regarding differences between dental stones, casts made by stones produced better results than those made by die stones in combination with reversible hydrocolloid impression materials.It was confirmed that evaluation by means of detail reproduction and surface roughness using a test block which met the requirements specified in ISO 1563 was an appropriate method for determining the compatibility of reversible hydrocolloid impressions and dental stones.

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On the base of CAM data produced in the previous paper, the fabrication of Ti crown was attempted by the miling method.First, a milling program which took into account the tool offset and tool interference was written for a ball end mill.A parallelpiped Ti block was fixed on a precise vise of a milling machine, and the outer crown was milled initially.The block was turned over, and the inner crown and the connective part were milled.Tool position adjustment after turning was precisely performed by imputting some parameter values.The contact portions remained so that they could support and connect the crown with Ti block.The crown fabricated was adapted on the stone die used for measurement.The accuracy of adaptation of the crown as milled was somewhat unsatisfactory, but after slight polishing, it was relatively improved.By serial studies, a CAD/CAM technique to fabricate Ti crowns was developed.

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We studied the changes of relative stresses and shear stress relaxation moduli of functional impression materials during setting and discussed the viscoelasticity using the Nutting equation.Stress relaxation were measured at 16, 23, 30 and 37℃, using the shear stress relaxation apparatus developed for six acrylic functional impression materials.From these findings, HS(HI-SOFT)and ST(Softone)showed large decreases in relative stress and rapid stress relaxation was induced.FI(FITT), LY(Lynal)and VG(Visco-gel)showed a high relaxation modulus of elasticity after setting and induction of stress relaxation was difficult.The exponential ratios(α/β)determined at 37℃ using the Nutting equation were 0.1 for FI and 0.2 for LY, and 0.5 for HS and ST.The former showed a higher elastic ratio and the latter showed a higher viscous ratio.The ratio of other materials were 0.3 or 0.4.

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N-methacryloyl-ω-amino acid(NMωA), which has a methacryloyl group and various methylene chain lengths, were synthesized.The influence of the methylene chain length in NMωA molecule and the water content in the N-methacryloyl-α-amino acid/ethanol-water primer solution on the tensile bond strength of the resin was investigated when exposed dentinal collagen was pre-treated with NMωA primer.Findings showed that bonding strength of the resin to dentin was strongly dependent on the methylene chain length in the NMωA molecule.NMωA, whose methylene chain length is 1, 3, 4 or 5, shows a adhesiveness.However, NMωA with a methylene chain lenght of 2 or 7 is not adhesive.In addition, the water content in NMαA primer affects the bonding strength of the resin.The bonding strength was increased by increasing the water content, reflecting an increase in the thickness of the inter-diffusion zone of the resin formed at the resin-dentin interface.

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