2019 年 60 巻 11 号 p. 2311-2318
A head-to-head comparison was made between an in-house-developed Ti–7.5Mo alloy and commonly-used grade-2 commercially pure titanium (CP-Ti) for dental casting applications. Experimental results indicated that all impurity concentrations, densities, linear thermal expansion coefficients and solid/liquid transition temperatures of Ti–7.5Mo and CP-Ti were similar. The 7-day total release of metal ions from immersed Ti–7.5Mo was acceptably low (10 µg/cm−2) with no harmful elements detected. Cytotoxicity testing indicated that Ti–7.5Mo had a cell viability of 82.5%, higher than the generally accepted value (70%). X-ray diffraction patterns indicated that Ti–7.5Mo was comprised primarily of α′′ phase with a small amount of β phase, while CP-Ti showed a monolithic α/α′ phase. Light and scanning electron microscopy revealed that CP-Ti had a typical plate-shaped morphology, while Ti–7.5Mo alloy was featured by its much finer acicular-shaped α′′ crystals along with equi-axed retained β grain boundaries. The castability value of Ti–7.5Mo was almost double that of CP-Ti. Both grinding and cutting tests indicated that Ti–7.5Mo had much better machinability than CP-Ti. Tensile testing indicated that Ti–7.5Mo had higher tensile strength, higher elongation and lower modulus (respectively 806 MPa, 42% and 70 GPa) than CP-Ti (respectively 571 MPa, 22% and 113 GPa). Bending data showed that Ti–7.5Mo had higher bending strength, lower modulus and much larger elastic recovery angle (respectively 1154.7 MPa, 75.8 GPa and 31.5°) than CP-Ti (respectively 919.5 MPa, 125 GPa and 2.8°). From all present data it was concluded that Ti–7.5Mo alloy would be a much better material than CP-Ti for removable partial denture application.
