Around 2009, in order to improve the optical properties of traditional tetragonal zirconia ceramics, by reducing the amount of alumina flux and appropriately increasing the sintering temperature to reduce the remaining pores in the zirconia ceramic material, zirconia basically achieved densification and sintering. Its semi-transparency can be appropriately improved, so that it has a light transmittance similar to that of dentin, and can be used for the production of full zirconia crowns and bridges in posterior teeth, avoiding the danger of porcelain chipping. This zirconia is called second-generation zirconia ceramics, also known as dense sintered tetragonal zirconia ceramics.
Since the crystal phase composition of the second-generation zirconia material is almost the same as that of the first-generation zirconia, the main crystal phase is still tetragonal zirconia (3Y-TZP), which maintains the high strength and high toughness of 3Y-TZP zirconia ceramics. When the first generation of white zirconia is gradually withdrawing from the market, compared with the third and fourth generation zirconia materials, the second generation zirconia has the best strength, so the second generation zirconia material is also called "" High-strength zirconia".
The second-generation zirconia all-ceramic materials generally use 3mol% (4~6wt%) of yttrium oxide as a stabilizer, the addition amount of alumina is reduced to less than 0.05wt%, or almost no addition, the main crystal phase is tetragonal zirconia (3Y-TZP), the grain size is 0.5μm~1.0μm, the content of cubic zirconia is less than 15%, and the semi-permeability is improved compared with the first generation of zirconia (studies show that the TP value of zirconia with a thickness of 1.0mm is 15~20), good mechanical properties, bending strength of 900~1300MPa, fracture toughness of about 3.5~4.5MPa.m1/2. Although the light transmittance of the second-generation zirconia material has been improved, it can basically meet the requirements of most restorations in the posterior tooth area with low aesthetic requirements, but if the second-generation zirconia material is used for full oxidation in the aesthetic area Zirconium repair, its semi-permeability still needs to be further improved.
The second-generation zirconia all-ceramic material can be used for all-zirconia crowns and bridges in the posterior area, all-ceramic bottom crowns in the anterior area, and three-unit or four-unit bridges in the anterior and posterior teeth. It is currently the main application material for all-zirconia restorations.
Representative products of the second generation zirconia ceramics include PrettauZirconia (PRT) (Zirkonzahn, Taufers, Italy), BruxzirZirconiaBRX (Glidewell Laboratories, Irvine, USA), WielandZenostarTranslucentZEN (IvoclarVivadent, PrincipalityofLiechtenstein), VitaYZHTWhiteandcolor (VYZa, VYZb) (VitaZahnfabrik), ICEZirconICE (Zirkonzahn, Taufers, Italy), LavaPlus (3MESPE), CerconHT (DentsplySirona), etc.