Why is CAD/CAM booming in the world?
It is important to know all the facts about Zirconium/CAD CAM restorations, so the practitioners know why it is gaining so much popularity in the world and they will be able to explain it well to their patients and enhance their dentistry results by using this sophisticated dental methodology.
What is CAD / CAM?
CAD stands for Computer-Aided Design and CAM denotes Computer-Aided Manufacturing. CAD/CAM is a technological breakthrough that has virtually dispelled the old methods of dental restorations using metal crowns and bridges. CAD CAM operates on a computer program, that first goes into effect by taking 3-D images of the patient’s teeth and gums. These images enable our professionals to design very precise and accurate dental restorations that are specific to each patient’s teeth and gums.
Once the final restoration is designed, the crown, inlay, onlay, veneer or bridge is milled from a single block of Zirconium material in a milling chamber. The restoration can then be customized with stains and glazes to create a more natural look, before being fired in an oven (similar to ceramics and pottery), and then finished and polished.
What is Zirconium/Zirconia?
Zirconium (ZirSiO4) belongs to the mineral group of silicates and was discovered in 1789 by the German chemist M.H.Klaproth. Zirconia has already been used for over 40 years for industrial purposes. It is exceptionally durable and 100% biocompatible. For this reason it is increasingly used in surgeries of ear, finger and hip prostheses. The biotechnical characteristics of zirconia result in high quality crowns, bridges and implants, with excellent bio-compatibility and aesthetic appearance. Zirconium belongs to a family of aluminum oxide.
Comparison of Zirconium/Cad Cam Crown with Porcelain Fused to Metal (PFM):
PFM crowns do not transmit light through the crown, resulting in a somewhat dull tooth appearance; people can identify the difference between natural tooth and PFM crown. Zirconia ceramic substrates, on the other hand, allow for light transmission, so the entire tooth and the surrounding tissue are illuminated and lifelike in appearance.
Dark Grey line on gums: In PFM, The metal that lies underneath the crown’s porcelain can sometimes be visualized as a dark line found right at the crown’s edge. If a person’s gums happen to recede, this dark line can show, thus spoiling the crown’s appearance. It will be visible in your smile and will give an unnatural appearance. In Zirconium restoration there will never be a gray line on the Gums, it permanently improves your look and your smile!
Zirconium crowns offer excellent marginal fit compared to PFM. This accurate fit offers financial benefits in crown and bridgework. The CAD/CAM technology ensures an accurate fit, the first time, virtually eliminating the need for costly remakes.
PFM may wear opposing teeth – The porcelain surface of a PFM crown can create (possibly significant) wear on those teeth that it bites on, or rubs against. A recent study found that the degree of wear on the opposing tooth was actually four times greater in dental porcelain than in polished, unglazed zirconia, suggesting that zirconia restorations are gentler in their functional interaction with natural dentition.
Strength and Ageing
All materials age, even metals. The flexural strength of metal before aging is about 500 MPa. Porcelain has 400 MPa and typical zirconia materials have a flexural strength of more than 1200 MPa. Often referred to as ‘white steel’, zirconia is just as strong and has a high fracture-resistance than porcelain restorations.
An idea about the strength of solid Zirconium crown: if strength of a standard .8 unit zirconium crown is considered 1200 MPa so a 2Mm solid zirconium strength can be about 3500 MPa which is more than 8 times stronger than Porcelain!!
Tissue sensitivity can be a common issue with PFM crowns and bridges. Base-metal crowns contain nickel, which can cause an allergic reaction in many people, especially women. Alternatively, zirconia is a biocompatible material, eliminating the risk of an allergic reaction and has been used with great success. zirconia shows excellent tissue response, when used in the mouth – gum tissue appears healthy and is pink in color.
Is Zirconia radioactive?
Every physical thing is radioactive! The human body radiates 6000 Bq(becquerel) of radioactivity. 1g of Zirconium dioxide measures about 0.4 Bq. A crown weighs approx. 1gr. Metal-ceramics restorations may radiate up to 2Bq/rg.