The use of CAD/CAM systems in dentistry and dental technology has become a common constitutive element of prosthetic restoration manufacturing. The list of ceramic materials for processing by CAD/CAM devices depends on the respective milling machine. Some milling machines are specifically designed for the production of zirconia frames, while others cover the complete palette of ceramic materials, from glass-ceramics to infiltration ceramics and oxide high-performance ceramics. 

Nowadays, the following standard ceramic materials for processing by CAD/CAM systems are available:

• Silica-based ceramics (a glassy matrix dental ceramic):
– Fine-particle feldspar ceramics.
– Leucite-reinforced ceramics.
– Lithium disilicate ceramics.

• Infiltration ceramics:
– In-Ceram Alumina (Al2O3).
– In-Ceram Zirconia (Al2O3, ZrO2).
– In-Ceram Spinell (MgAl2O4).

• Oxide crystalline ceramics:
– Zirconium dioxide.
– Aluminum oxide.

In this post we will focus on silica-based ceramics. From among grindable silica-based ceramic blocks, one may choose feldspathic porcelain blocks (eg, Vita Mark II, Vita), leucite-reinforced (eg, Empress CAD, Ivoclar Vivadent), and lithium disilicate ceramic blocks (eg, IPS e.max CAD, Ivoclar Vivadent). As a result of their relatively high proportion of glass, these ceramics are, in contrast to oxide ceramics, etchable with hydrofluoric acid, and can thus be inserted very well using adhesive systems. The currently available ceramic blocks can be mono- or polychromatic.

Vita is the most experienced manufacturer of ceramic blocks for CAD/CAM systems. Since the CEREC system was introduced to the market in 1985, VITABLOC ceramics have displayed a success rate of 92% (studies available over a 5-year period). 

VITABLOCS Mark II and CEREC Blocs are made of fine-structure feldspar ceramics, and their abrasive properties are similar to those of natural enamel. They are highly translucent and, due to their exceptional polishing properties, most often do not require glazing.
Besides the properties described for VITABLOCS Mark II, 

VITABLOCS Triluxe has three layers with different degrees of color saturation in one block, thus being more likely to replicate tooth structure in terms of translucency and color saturation. 

VITABLOCS Triluxe Forte display softer nuances of color transition from the enamel to the neck, with enhanced emphasis on color shades and translucency.
VITABLOCS Real Life display inside individualization of color shades, which enables placing the final restoration during the milling phase so as to fully cover the prepared abutment with a dentin-simulating ceramic structure. The flexural strength of the aforementioned blocks is 150 MPa. 

IPS Empress CAD
IPS Empress CAD is a leucite-reinforced glass-ceramic with a flexural strength of 160 MPa and exceptional color properties. Therefore, the blocks may be chosen according to the preferred translucency (high translucency or low translucency) and shade in the classical A to D shade guide, as well as shades for whitened teeth. High-translucency blocks are mainly used for smaller restorations (inlays, onlays) due to their true-to-nature chameleon effect, whereas low-translucency blocks are suitable for the fabrication of crowns, due to their chroma and brightness values.
Besides the aforementioned benefits, IPS Empress CAD Multi are polychromatic, with high brightness and translucency values. They also have a lifelike chameleon effect and fluorescence similar to the neighboring dental structures. 

IPS e.max CAD blocks
 are made of lithium disilicate and have a flexural strength of 360 MPa. They combine strength, efficiency and esthetics, making them chiefly suited for lateral crowns and up to four-unit posterior bridges (in the latter case the CAD-on technique is used, by which the ceramic superstructure is milled over a previously fabricated zirconium dioxide framework). They have exceptional color stability, high abrasion resistance over time, and excellent esthetics, which makes them widely popular.
Beside the option of choosing between high-translucency and low-translucency blocks described for IPS Empress CAD, there are also medium-opacity blocks, which are used to mask colored abutments. Due to their properties of strength and brightness, IPS e.max Impulse blocks are best suited for partial crowns and very thin veneers.
It should be taken into consideration that, in contrast with the other materials that do not go through a crystallization stage, these blocks do go through a crystallization stage of about 30 mins after milling. They initially exhibit a bluish color and are better milled in their “soft” state. Consequently, an in-office ceramic furnace is required.

📝Any restoration fabricated from the aforementioned materials can be bonded because they react with hydrofluoric acid. Furthermore, blocks of various sizes are available, according to clinical indications.

Prosthetic restorations " Temporary "
Another category of prosthetic restorations produced with chairside CAD/CAM technology are provisional restorations. Either single crowns or bridges, sometimes for longer-wear periods, can be fabricated from various materials supplied by manufacturers (eg, Vita CAD Temp Monocolor or Multricolor, with a flexural strength of 80 MPa, or Telio CAD, Ivoclar Vivadent, to be used for bridges with up to two pontics, and wear periods of up to 12 months). 

New materials have recently been developed, such as nanoceramic, supplied by 3M ESPE, and Vita Enamic, fabricated by Vita. 

Nanoceramic is a mixture of composite resin and ceramic. Like a composite, it does not break and is fracture resistant, at the same time preserving its shine for a long-term esthetic appearance. The material does not require glazing after milling because it can be polished. Its flexural strength is 200 MPa, higher than that of the previously described materials (except for IPS e.max CAD, which requires crystallization after milling). The material is best suited for crowns, implants, inlays, onlays, and veneers. The product warranty period is limited to 10 years. 

Vita Enamic is a hybrid ceramic with a dual network structure, the dominant ceramic network being reinforced by a polymer network, with each network penetrating the other to create a hybrid material that exhibits the positive characteristics of both a ceramic and a composite. This material is perfectly suited for crown restorations in the posterior area and minimally invasive restorations.

Vita Suprinity is a zirconia-reinforced lithium silicate glass-ceramic, with an average flexural strength of 494.5 MPa, which indicates this material for the fabrication of inlays, onlays, partial crowns, veneers, anterior and posterior crowns, and anterior and posterior single-tooth restorations on implant abutments. Crystallization is required after the milling process, following which the material can be individualized or characterized with special ceramic materials. 

Celtra Duo (Dentsply Sirona) was introduced in 2012 as a zirconia-reinforced lithium silicate (ZLS). The ZLS microstructure has a high content of ultra-fine glass-ceramic crystals. The manufacturer provides Celtro Duo in a fully crystallized state that may be either hand-polished or  glaze-fired in a ceramic furnace prior to delivery, that's why it was so called ''Duo'''. Hand polishing of the restorations results in a material that has a flexural strength of 210 MPa, while glazing it in a porcelain oven results in a restoration with a flexural strength of 370 MPa. It can be used for the fabrication of inlays, onlays, veneers, anterior and posterior crowns. 
Both IPS e.max CAD and Celtra Duo are also available to dental laboratories as press-fit ingots.