Zirconia ceramics with phase transformation toughening and microcrack toughening, so has high strength and toughness, known as 'ceramic steel', its fracture toughness is the highest in all ceramic, but the highest hardness is alumina ceramic, zirconia it has the features: 1, zirconia ceramic hardness close to the natural diamond, lighter than metal, has never wear, don't change color gem features such as; 2. Extremely high hardness