Porcelain fused to metal full crowns because of its high strength, and other characteristics for most patients to accept, but its metal base easily oxidized to form gray oxide, scattered in the deposit to the gingival margin, causing gingival gray, affecting the aesthetic, metal porcelain crowns may have an irritating effect on the gums, individual patients will appear swollen gums, bleeding, allergies, it is difficult to achieve clinical requirements. Aesthetically speaking, due to the presence of metal base crowns, it is necessary to cover with shaded porcelain, which makes porcelain crowns produce a certain degree of light blocking effect, and thus deviate in aesthetics. Zirconia all-porcelain crowns have a certain degree of permeability due to the absence of metal base crowns, thus offering the possibility of aesthetic restorations. In addition, zirconia all-ceramic crowns have many advantages: 1, excellent mechanical properties, with a bending strength of more than 900 MPa, and thus can also be used for posterior teeth and porcelain bridge restorations of more than 6 units. 2, good biocompatibility: zirconia all-ceramic crown itself metal-free, in the latest published American Clinical Research Association CRAI clinical evaluation report, concluded that zirconia all-ceramic crown restoration can exclude metal allergic reaction, its biocompatibility is good, better than a variety of metal alloys, including gold. 3, zirconia on the x-ray without any obstruction set into the zirconia porcelain teeth, if later need to carry out cranial x-ray, CT, MRI examination also do not need to remove the dentures, save a lot of trouble. Of course, there are now many all-porcelain restoration materials, its beautiful and realistic restoration effect has long been recognized by the majority of doctors and patients, the current all-porcelain materials, such as white garnet, lithium-based porcelain, aluminum oxide, zirconia, etc., production methods are also different, such as infiltration ceramic, hot press casting ceramic, porcelain deposition, computer-aided design and computer-aided production, but comparatively speaking, in all all-porcelain restoration materials, to Zirconia has the highest flexural strength.