It is quite common that I try in an all porcelain restoration after the glass has been etched with hydrofluoric acid. I have asked that any restorations I get back from the laboratory are already etched, and for the units we create in office, my assistant will often etch them before I am back with the patient for try-in. Many of you may be asking yourselves, why I don’t just wait and etch the glass after try-in when I am ready to begin bonding. There is no correct answer about this, I simply prefer not to have to deal with hydrofluoric acid chairside, and stopped doing so once I learned how to clean the porcelain after try-in.
Once the glass has been etched, we do not have to etch it again if it goes in the mouth, and this can actually be detrimental to the integrity of the porcelain. Our concern once we try the restoration in the mouth is contamination by saliva, blood, debris and handpiece oil. The best tool in our offices for removing all of these forms of debris is always available and easy to use, phosphoric acid etchant. When I am ready to begin bonding, the first thing I do is coat the intaglio surface of the restoration with phosphoric acid, and allow it to sit for 30-45 seconds. The gel is then rinsed off thoroughly. If you dry and observe the restoration you my notice a layer of mineral deposit. To finish the cleaning process we place the restoration in a Ziploc bag along with distilled water and place in the ultrasonic for 2-3 minutes. Finally dry the restoration with clean air, not using your air water syringe, to prevent recontaminating this fresh surface. The restoration is now ready for the application of porcelain conditioner.