The rate of vacant space and compression strain on heating were evaluated as parameters of cushioning ability in 14 ceramic liners(A:rock wool type, B:ceramic fiber low temperature type, C:ceramic fiber standard type, D:ceramic fiber low temperature standard type, and E:kaolin type)and 3 asbestos ribbons.Concerning the rate of vacant space on heating, the liners could be classified into 2 groups:one that increased significantly and one that increased slightly between 200-400℃, or one that increased slightly and one that was unchanged over 400℃.Concerning compression strain on heating, the liners could be classified into 2 groups:one that decreased slightly and one that was almost unchanged at 200℃, or one that increased with temperature and one that was almost unchanged over 200℃.The coefficient of correlation between the rate of vacant space and the compression strain on heating was significant.

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This study evaluated the thermal properties of resin-modified glass ionomer cement(RMGC)s compared with those of conventional glass ionomer cements, a resin cement, a composite resin and human enamel and dentin.Thermal properties were measured by TC-2000L(Shinku-riko)using xenon flash as the light source, and thermal conductivity of RMGCs for luting were 0.437-0.440Wm^<-1>K^<-1> and those of RMGCs for filling were 0.326-0.500Wm^<-1>K^<-1>.It was clarified that thermal conductivity of RMGCs were lower than that of human dentin.

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Agar/alginate combined impressions, with 4 brands of agar impression materials, were immersed in solutions of 0.5% sodium hypochlorite for 15 minutes and 2% alkaline or acidic glutaraldehyde for 30 minutes.The impressions were poured with die stone, then surface roughness and dimensional accuracy were measured.A 15-minute immersion of combined impressions in 0.5% sodium hypochlorite did not adversely affect the surface roughness and dimensional accuracy of stone dies.However, 30-minute immersion of them in alkaline glutaraldehyde solutions increased the surface roughness of stone dies.

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Effect of pretreatment with an experimental tooth conditioner, <Phytic acid-SnF_2>primer, on bonding of three conventional and three light-cured glass ionomer cements to tooth substrates was evaluated.This primer requires a 2-step treatment.First, teeth were treated with 7% phytic acid solution, rinsed with water, and then air-dried.Secondly, teeth were treated with 3% SnF_2 solution, rinsed with water and then air-dried.The shear bond strengths of ionomer cements to bovine dentin and enamel treated with this primer or with 7% phytic acid solution alone or according to manufacturers' directions were determined and results were compared with each other.In five cements, the highest bond strengths were obtained after treatment with<Phytic acid-SnF_2>primer.Especially, the treatment effect was high in the light-cured type.After thermal cycling(4〜60℃)500 times, bond strengths hardly decreased.It was suggested that some chemical interaction between polycarboxylic acid in the cements and Sn^<2+> fixed on the tooth surface contributed to the bonding of ionomer cement to tooth substrates.

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A new titanium alloy, Ti-5Al-13Ta, was designed for dental casting;its mechanical properties and corrosion resistance were investigated.The proof stress and the tensile strength of Ti-5Al-13Ta alloy were somewhat lower than those of Ti-6Al-4V or Ti-6Al-7Nb alloy but higher than those of Grade 3 titanium.However, the elongation of Ti-5Al-13Ta alloy was noticeably higher than that of the other two titanium alloys.This tendency appeared to be related to atomic numbers of the third element from the column Va.α and βphases were detected in these three alloys by XRD, which was thought to influence on their mechanical properties.These alloys also showed good corrosion resistance in cyclic voltammetry and immersion test.From these results, Ti-5Al-13Ta alloy was considered applicable to dental casting.

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The Ni-Ti alloy characterized by its shape memory and super-elasticity has been applied to dental use.In this study, the corrosion behavior and cytotoxicity of Ni-Ti wire were examined.There were no Ti ions released from pure titanium or Ni-Ti alloy when specimens were dynamically immersed in saline solution or MEM.However, the Ni-Ti alloy released a small amount of Ni in MEM and inhibited the cell growth, although its inhibitory effect was significantly smaller than those of the non-precious dental alloys.In 1% lactic acid solution, Ti was released from pure titanium and Ni-Ti alloy and much amount of Ni from the latter, which potentially showed almost the same cell growth inhibition with the non-precious dental alloys.

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