Studies on Improvement of Properties and Clinical Qpplication of Pure Titanium Restoration

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1) Internal porositiesThe amount of prosity of titanium casting was estimated from the densi determination of any specimen,and radiographic examinations were employed to observe the internal porosities of the casting.The amount of porosity was independent on the mold temperature and the magnitude of the casting pressure. Hoeever,it was markedly influenced by the permeability of the mold materials and the suction during the application of castig pressure. It was showed that the amount the porosity decreased with decreasing the permeability of the mold materials. In the case of the high permeability mold materials,the casting pressure with suction developed the internal porosities much more than without suction.2) GastabilityThe castability values of pure titanium was lower at room temperature than at 8000゜C. Increasing the casting pressre caused an increase in the castability value and the suction was effective on the gain. The value decreased as the permeability of the mold materials w … More as lowered.These result suggest that the casting procedure for preventing the porosities of titanium castings is unsuitable for increasing the castability. Therefore,it is most effective to apply the large castung perssure without suction. Employing a diaphram between the melting chamber and the casting chamber of the vacuum!argon pressure casting machine was very effective on the gain of the castability.3) Improvement of fitness on castingsThe practical improvement of dimensional fitness between titanium castin and abutment was achieved by the oxidizing expansion of Zr metal powder mixed in a magnesia invesment during firing up to 800゜C. This magnesia investment was used as a face-coating investment and the dental phosphate-bonded investment was used as a outer investment for the titanium casting crown.4) Glinical application of pure titanium restorationSince 1982,more than one hundred restorations of pure titanium have bee used chinically. There were no problem in the adhesion of plaque, discoloration and occlusal wear to the titanium restorations.There were useful for prosthodontic evaluation in retentive condition on resin veneered titanium cast crown,and bending strength and corrosion on titanium post core. Less