| 摘要 |
<p>Provided is an orthodontic bracket with high strength and high translucency, which can be processed into a complicated shape, which can be made in a shape closer to that of a metal bracket, and which maintains excellent translucency. The orthodontic bracket is comprised of a translucent ceramic containing at least 99.5 wt% of alumina, and having an absorption/scattering coefficient of at most 2.8 mm -1 for visible light at a wavelength of 550 nm and a bending strength of at least 700 MPa. This bracket is obtained, for example, by sintering a molded body of highly-pure alumina fine powder at a temperature of from 1,200 to 1,300
C to obtain a sintered body composed of crystals having a relative density of from 96 to 99.5% and an average crystal grain size of at most 1 µm, and thereafter subjecting the sintered body to an HIP treatment at a temperature of from 1,200 to 1,350
C and under a pressure of at least 50 MPa.</p> |
