Until recently, providing a CAD CAM monolithic restoration always resulted in aesthetic compromise. Through extensive economic investment, research and development by a few select companies this is no longer the case. Until now, the industry standard for adequate strength and best aesthetics in a monolithic restoration had been lithium disilicate (LD). We have now reached the tipping point. Yes, CAD CAM now enables laboratory technicians to produce zirconia restorations that are more aesthetic and 50% stronger than lithium disilicate.
Taking a close look at two disc manufacturers, Noritake (of Japan) and Amann Girrbach (of Austria), the tipping point for highly aesthetic monolithic CAD CAM restorations is here. The discs I’m referring to are multi-colored or multi-layered, meaning the bottom of the discs are more chromatic or darker and the top is more translucent or lighter. The discs have been designed with several layers of color with blending of the powder between each layer prior to pressing into disc form.
Katana zirconia from Noritake includes an “UTML” disc. This disc has increased chroma in the bottom and increased translucency in the top. The material has a flexural strength of 557 MPa. and is incredibly aesthetic. STML can be milled in any mill used for zirconia and sintered in most sintering furnaces.
Amann Girrbach has developed “Zolid FX Multi”, another multi-layered zirconia disc. These discs have been similarly designed with layers of pre-shaded colors, but include more layers in each disc. This enables the lab to obtain 2 shades from each disc. For instance, when using the shade A2 disc one can nest the unit in the bottom of the disc and obtain an A3 nested in the top and it results in shade A2. With a flexural strength of 600 MPa this material is 50% stronger than lithium disilicate and far more aesthetic.
Today, the vast majority of dental crowns prescribed in North America are monolithic. That said, we have definitely reached the tipping point with both improved strength and superior aesthetics with CAD CAM and zirconia.
The photo above is a case where we made #6-8 (11,12,13) using Zolid FX Multi shade A2, units 9-11 (21,22,23) were fabricated using e.max HT press shade A2. The zirconia was milled sintered and glazed. The e.max units were and glazed. You can be the judge.
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