An important step in bonding in an IPS e.max ( Lithium Disilicate) restoration is to prepare the intaglio surface of the glass by etching with hydrofluoric acid. The quality of the bond is dependent on the effectiveness of how the glass is etched, so understanding the manufacture recommendations is critical. Lithium Disilicate has very different etching protocols then other porcelain restorations due to it’s unique crystalline structure and chemistry.
Over etched appearance of Lithium Disilicate
There are multiple different protocols being discussed for this product when I attend lectures, it seems between this being a relatively new material for many practitioners, and the difference from the protocol for other porcelain products confusion has resulted. Ivoclar recommends preparing the glass with IPS ceramic Etching Gel, a 5% hydrofluoric acid, for a maximum of 20 seconds. Do not rely on the appearance of the internal surface as an indicator of adequate etching, as a frosty appearance actually indicates over-etching..
When etching porcelain the old adage of “if a little is good more is better” does not apply. Over-etching Lithium Disilicate, due to it’s filler content and crystalline matrix, can be very detrimental to its strength and the long term success of the restoration. To ensure that you are not over-etching, first confirm for a lab processed restoration whether it has been etched by the lab. If you are etching in your office, use the correct strength of hydrofluoric acid and a timer so you rinse after a twenty second exposure time. A restoration that is tried in the mouth after etching should not be exposed again to hydrofluoric acid, but cleaned prior to the application of porcelain conditioner to remove saliva and debris.
Buzz, Gloria, Carlo and I were just at Ivoclar in Lichtenstein last Wednesday (or Thursday, I forget!). They talked about just what you wrote about and compared it to zirconia, etc. Great time with Ivoclar and FANTASTIC time with everyone touring across all of Switzerland! Breathtaking scenary and even better company!
Jay
I’ll be with Buzz in a month or so and hopefully he will have photos from the trip. I am jealous that you got to visit Ivoclar, I bet that was really interesting. Hope all is well and we get to see one another some time soon!
Thanks a lot for sharing the information will follow the protocol . Always look forward to read your articles they have a lot of ideas and info on techniques please keep writing.
Thanks for your special tidbit. Keep it coming. JK
Dear Lee Ann,
thank you very much for sharing and providing some insight to this relatively new material.
do you find a difference between etching pressed and CAD emax? I found the pressed emax becomes frosty more easily than the CAD. do you find this in your practice too?
thank you.
I have not personally seen a difference, but I will check this out with Ivoclar and find out.
I spoke with Dr. Sibel Antonson from Ivoclar, and she confirms that the etching protocol and the appearance is identical between the cad and the presses lithium Disilicate.
What happens if you are overetching by mistake the lithium disicate – I mean what will be the clinical protocol in this situation?
Thanks
The challenge is there really isn’t a protocol. The over-etched ceramic is weakened and can not be infiltrated properly by the resin cement. Some folks have advocated scrubbing the inside with rubbing alcohol to remove the frosty layer, re-etching with MonoBond Etch and Prime and seating. The challenge is then that you have a thicker resin layer and less precise fit tot he ceramics, which puts more load on the resin interface and could result in pre-mature de=bonding.
We too notice a difference in etch patter between presses and CAD. Its very interesting Ivocalr cited they are identical when so many doctors note a visual difference.
We have been using Ivoclars HF 20 sec etch exclusively on our IPS e.Max Cad since we started using Cerec years ago. Recently we have have a series of different restoration types (veneer, full contour, crown etc.) debond. Every time the restoration is complete clean on the intaglio, all of the resin in on the prep. We use variolink for veneers and panavia for the crowns but the etch and bond steps are the same.
We do also use an outside lab for pressed veneers of which none have debonded. they come lab etched and very very frosty in comparison to the CAD. Even with heavy bruxers the restorations are more likely to crack and still not debond.
Can anyone help shed some light on this?
I just gave a lecture on CAD/CAM today and the topic of etch time for eMax came up. While there was a general consensus that 20 seconds is indeed the max time, there didn’t seem to be an agreement that necessarily anything adverse clinically has been proven to result from etching more than 20 seconds. In other words it seems to be based more in scientific theory than clinical reality. Any thoughts on this?