Choosing the right kind of ceramic material that provides the optimal strength and esthetics, is one of the hardest decisions for a dentist to make. Nowadays, lithium disilicate (Emax) and zirconia (Bruxzir and Crystal) ceramics are being most commonly used for the fabrication of different types of dental prostheses. But which of these materials should your prefer? This article provides you with a detailed comparison between the lithium disilicate and zirconia crowns.
Emax v. Zirconia Crowns; Difference in Composition
Lithium disilicate, or Emax crowns, are a type of a ceramic that is used in the fabrication of all-ceramic dental prostheses, owing to their excellent esthetics, durability and strength. On the other hand, zirconia, which is basically a crystalline structure consisting of zirconium oxide, is a ceramic material that surpasses the lithium disilicate ceramics in durability, fracture resistance and strength. However, due to their extremely high strength and highly crystalline nature, zirconia crowns appear opaque and have to be glazed with another material to provide the required esthetics.
Emax vs Zirconia Ceramics; How are they Prepared?
The processing methods for both types of ceramics is essentially the same. The fabrication of lithium disilicate ceramic prostheses involves the use of ceramic blanks that can then be processed into the desired shape through milling or through CAD CAM. The Bruxzir and Crystal zirconia based ceramics are provided in the form of isostatically pressed blanks that are then milled into the desired form and shape.
Lithium Disilicate versus Zirconia; Which is Stronger?
Zirconia (Bruxzir and crystal brands) is much stronger than lithium disilicate or Emax. One of the reasons behind the superior strength of zirconia is its highly crystalline nature as well as the ability to undergo ‘transformational toughening” when certain metallic oxides, such as yttrium oxide (Y2O3) are added to the crystals. This phenomenon ensures that zirconia quickly undergoes a change in its crystalline nature whenever a force is exerted on the material, thereby enhancing its fracture resistance.
Emax Versus Zirconia; the Indications
Owing to the better translucency of the Emax ceramics, they are highly suitable for use as anterior crown and bridge materials. Their excellent translucency ensures that the lithium disilicate ceramic prostheses exactly match the color and shade of the anterior teeth. On the other hand, the zirconia based ceramics are not commonly used for the fabrication of anterior prosthesis, owing to their very high opacity. The zirconia based ceramics are commonly used for the fabrication of single, two and three unit prostheses in the posterior region, especially in the high stress bearing molar region of the oral cavity.
Lithium Disilicate versus Zirconia Ceramics; A comparison of their Esthetics
Historically, lithium disilicate crowns provided esthetic results superior to zirconia due to their ability to provide the required translucency, shade and color of the prosthesis according to each clinical situation. However, remarkable progress has been made to overcome the esthetics concerns of zirconia, such as its limited shades, colors and opaque appearance. And with the announcement of super-translucent anterior zirconia, such as Crystal Anterior, there is today a Zirconia that rivals the esthetic qualities of e.max and empress.