Zirconia made a significant appearance on the dental horizon about 5 years ago. It provided an alternative for all ceramic crowns and bridges. Today, a milling procedure is the only reliable way to create zirconia restorative components for dental use. The availability of computer numerical controlled machines (CNC) allows for highly automated end-to-end component design using computer aided design and computer aided manufacture (CAD/CAM) programs. The programs produce a computer file that is interpreted to extract the commands needed to operate a particular machine, and then loaded into the CNC machines for production of the restoration coping or framework.
There is also the possibility of producing the same results with an analogue copy-mill system.
Zirconium dioxide (ZrO2), sometimes known as zirconia, is a white crystalline oxide of zirconium and is one of the most studied ceramic materials.
Zirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium.
Despite being oxide of the metal, Zirconium dioxide is in the family of the full ceramics, more specifically, the oxide ceramics, also classified as technical ceramics. Oxide ceramics are polycrystalline materials that are composed of oxides that do not degrade during sintering.
Zirconia as a pure oxide does not occur in nature. It’s most naturally occurring form, with a monoclinic crystalline structure, is the rare mineral baddeleyite. It is also found in zircon (ZrSiO4). Baddeleyite and zircon form the main sources for the material. Of the two, zircon (zircon sand) is by far the most widespread but it is less pure (its purity depends on where it has been mined) and requires a significant amount of processing to yield zirconia.