We all use ceramic restorations in our practices and will always complete a try-in step before bonding the restoration to the tooth. Common practice says if there’s blood on the intaglio surface we have to re-etch it, but if it doesn’t have copious amounts of saliva on it, we might just wash and dry it then apply silane. But are we actually doing the right thing?

We asked dentists what their protocol is and many don’t necessarily clean the crown after trying. They didn’t have a clear understanding of the advantage of cleaning and silanating the restoration.

A scientific study back in 2009 looked at the efficacy of etching/silane vs Ivoclean/silane and concluded that these restorations are best cleaned with either 37 percent phosphoric acid (e.g. Total Etch gel) or a 5 percent hydrofluoric acid.

The part that many are missing is that getting any saliva contamination is harmful, and here’s why: saliva contains alkaline phosphatase that more or less reacts with the surfaces of the crown rendering it inert to your primer silane. Therefore, you HAVE to clean it. Using acid etch will render it clean and increase the bonding strength – as long as it wasn’t pre-etched.

If your restoration was pre-etched from the lab, it still requires cleaning, but you don’t want to re-etch it. Doing so removes more filler particles and renders the restoration less strong. In this case, you will want to use Ivoclean. Ivoclean consists of an alkaline suspension of zirconium oxide particles in water (which is why you have to shake the bottle well). It is strongly alkaline and thus corrosive, so you have to be really careful to wear gloves and eye protection.

The concentration and size of the particles render them more attractive to the phosphate contaminants. They absorb them like a sponge and leave behind a clean oxide surface. It in essence becomes an acid-base reaction.

HERE’S THE TAKE HOME LESSON

You can have your lab etch your restorations, but if you are trying it in first, which you undoubtedly will, you have to re-clean it. Since you don’t want to re-etch it, which will remove too many of the filler particles, you need to use Ivoclean. If you have chosen not to have your lab etch the restoration, you can etch it yourself but will need to know your ceramic as well as the concentration and time of the acid that the manufacturer recommends.

If you follow these recommendations, your incidence for crowns coming off will be greatly reduced and your satisfaction for doing all ceramic restorations will escalate.

Adopted from a post by Mary Ann Salcetti. Edited by Nima Dayani, DDS, MS

Author: Nima Dayani
January 6, 2019
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