All-ceramic crowns and bridges are non-removable prosthetic devices which are the most aesthetic from all. They are metal-free devices and are practically visually indistinguishable from natural teeth and this is due to the fact that when the ceramics is not backed by metal, it refracts the light just like natural teeth. Another great advantage is that all ceramic crowns do not cause allergies.
They are two main types – the first type is based on zirconium oxide (so-called “zirconia crowns” that represent a zirconium base upon which the ceramics is deposited), they are used for posterior teeth and for large bridges. The second type is IPS Emax ceramics, which is a real and pure ceramic material, which resembles the properties of natural teeth. Crowns and bridges from pure ceramics can be made for both alive and dead teeth. They have very high strength (360-400 MPa for IPS Emax compared to 70 MPa for the cermet) and can cover chewing teeth. Similarly to the cermet, this type of crowns does not retain dental plaque and tartar. Ceramic crowns are extremely comfortable, and the patient does not feel any difference from natural teeth. Another major advantage of ceramic crowns is that they do not change the colour of the gum, as it happens with some metal-ceramic crowns.
The biggest advantage of ceramic crowns (IPS Emax) is the possibility to cement the crown to the tooth stump adhesively. Adhesive cementation is a procedure, in which the surface of the tooth stump and the inside of the crown are treated with special chemical agents, which prepare the surfaces for partial chemical bonding with the adhesive cement. This leads to exceptional strength of the structures and almost reduced to zero possibility of detachment and fall of the crown.
Making crowns and bridges from pure ceramics can be done in two ways.
One of them is the standard way for making crowns by a dental technician, but instead of a metal one, a zirconium cap is used.
The second option for making ceramic crowns is through CAD/CAM technology.
This is a new technology, where the crown is made of special IPS Emax ceramic block that is shaped by a special robot to the required shape. In CAD/CAM technology a tooth impression is taken with a special 3D camera instead of silicone that turns it into a 3D computer model of the tooth stump.
Then using special software, the crown is molded and the selected ceramic block is milled by the robot. The milled crown is extremely accurate. The crown is placed in the patient’s mouth to ensure that it fits, and then the device is coloured and polished.
Another feature of the crowns of pure ceramics is that they are glued with special high-strength cements, which have also different colours and are double hardening (self-hardening and hardening under the effect of light from a photo lamp). The only disadvantage of this type of crown is their higher price, due to the use of expensive and high-quality materials and the method of fabrication. In summary, it can be said that IPS Emax is the most aesthetic and the best material for making crowns and bridges in modern dentistry.