PURPOSE: To provide an orthodontics bracket excellent in mechanical property, by making the dentition straightening bracket made of partially-stabilized zirconia sintered body and making the sintered body contains a specified ratio of zirconia having a crystal structure of tetragonal system, and contains substantially no zirconia having the crystal structure of cubic system.
CONSTITUTION: An orthodontics bracket is made of a partially-stabilized zirconia sintered body, and the sintered body does not substantially contain zirconia having a crystal structure of cubic system and contains 95.5 mole % and more and 99 mole % and less of zirconia having the crystal structure of tetragonal system. Here, the partially stabilized zirconia is composed of mainly ZrO2 and a partial stabilizing agent, and molar radio of ZrO2/partial stabilizing agent is in a range of 97.8/2.2 to 98.4/1.6, and the partially-stabilized zirconia contains totally 98.5 to 99.7weight% of ZrO2 plus the partially-stabilized agent. This dentition straightening bracket has high initial strength and toughness and excellent estheticism and highly stable mechanical property after a long term usage.
YOSHIDA MASAHIRO
SHIRONITA AKIRA
HINO TAKASHI
SHINAGAWA REFRACTORIES CO
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