Table 2. Current classification of the zirconia-based on the yttria content and indications.

Types	Indications
Type 1A: 3Y-TZP(conventional) (1) Ceramill Zi (2) Vita YZ T (3) Cercon base (4) Kantana LT (5) Emax Zir CAD LT	–Substructure –Custom abutment –Single-tooth and up to 14-unit bridges on screw-retained restorations in the anterior and posterior tooth region (primary telescopic)
Type 1B: 3Y-TZP with reduced alumina (1) Vita YZ HT (2) Cercon HT (3) Lava Plus (4) Lava chairside (5) GC Standard Translucency (ST) (6) GC High Translucency (HT) (7) GC Ultra High Translucency (UHT) (8) Nexx Zr S (9) Nexx Zr T (10) DD Bio Z High Strength (HS) (11) DD Bio ZX2 High Translucent (HT) (12) Katana HT (13) Katana HT ML (14) E Max Zr CAD MO	–Substructure –Custom abutment –Single-tooth and up to 14-unit bridges on screw-retained restorations in the anterior and posterior tooth region (primary telescopic)
Type 2: 4Y-TZP (1) Zolid gen x (2) Zolid drs multilayer (3) Zolid ht+ preshades (4) Zolid ht+ white (5) Vita YZ ST (6) Vita YZ ST Multicolor (7) NexxZr+: Hight Translucent (8) DD cube ONE® –High Translucent Plus (HT+) (9) Katana STML (10) Emax Zircad MT	–Single-tooth and up to 14-unit bridges on screw-retained restorations in the anterior and posterior region –Inlay, onlay, tabletop
Type 3: 5Y-TZP (1) Ceramill Zolid Fx White (2) Ceramill Zolid Fx Multilayers (3) Vita YZ XT (4) YZ XT Multicolors (5) Cercon XT (6) Cercon XT ML (7) LAVA Esthetic (8) DD cubeX2® –Super High Translucent (SHT) (9) Katana UTML	− Anatomical crowns and bridges (<3 units extending to the second premolar region)
Type 4: Combination of 3Y/ 4Y and 5Y-TZP (1) NexxZr T Multi: Translucent (2) NexxZr Multi: High Translucent (3) Katana YML (4) Emax Zir CAD MT Multi	–Single unit –Multiple unit bridge