We use the term etching in regards to the intaglio of a restoration to describe how we prepare the material before bonding or cementation. The semantics challenge with this is that etching for many of us implies the use of an acid, and that is not always the case. Zirconia is a primary example of an all ceramic restorative material that is NOT prepared with an acid.
Zirconia restorations do not have to be “etched” or the internal surfaces treated if your intention is to cement the restoration in place. If the prepared tooth has adequate retention form and resistance form then traditional cements or luting agents can be used. After the restoration is tried in the internal surface of the restoration can be cleaned with a Ivoclean for 30 seconds and then rinsed and dried. Cementation can then be accomplished with a glass ionomer, resin modified glass ionomer or self-adhesive cement.
Alternatively if your aim is to utilize adhesive retention then the zirconia needs to be prepared or “etched” This preparation can be done prior to try in, as long as the restoration is cleaned well after to remove saliva, blood or oils. You can also try the restoration in first and then clean and prepare the zirconia for bonding. Zirconia is “etched” using air abrasion or sand blasting. You can use aluminum oxide in a particle size of 30-50 microns, or cojet powder at 30-40 psi of pressure and a distance of 10mm. There is some research that sand blasting zirconia can increase the risk of failure under occlusal load due to weakening of the material. Therefore it is critical to sand blast with the correct particle size and pressure.