A Masterful Combination Of CAD/CAM And Manual Skills
August 26, 2021
Just a little while ago, I was asked if our Lab did feldspathic restorations. I said yes of course, while thinking to myself, ” that seems like a kind of old school restorative approach.” However, clearly not lost or forgotten. Let’s go pick ole Johnny’s brain about this.
Now of course he didn’t just give up all the answers. I still had to do my homework and ask the questions.
Feldspath restorations are beautiful works of art. It takes a skilled ceramicist and doctor plus an ideal patient for a long term outcome of this type of restoration. Some pros.These can be done with little to no tooth preparation. They are highly esthetic and life like and have a super strong enamel bond.
But just like a tiny porcelain cup, they are very fragile. Strength only around 70 -90 mpa.
With out any prep retention, flexural tooth movements and oral habits can compromise integrity and adhesion.
Moving along with our desire for stronger, esthetic dentistry, we come onto pressable lithium disilicate.
This material checks the box of making a stronger restorations at  400 – 500 mpa. Excellent accuracy, and strong enough to be considered for posterior restorations. (* when certain considerations are taken into account) You can get away with more conservative tooth reduction as well. It is quite a nice option for inlays, onlays, full or 3/4 coverage for the bicuspids or a first molar in a patient with a ‘kind’ occlusion. These restorations do come out looking quite beautiful as is, but nice staining and glazing elevates their authentic appearance so much more! Not to mention, the lithium disilicate takes on feldspath layering very predictably. The Investing technique with pressable ceramics is easier and more predictable than building a restoration layer by layer with powder. A very finicky process for sure. But for some time now,  to improve on this even more, we have the option of milling lithium disilicate blocks.
The lessons I get from John always boil down to restoration strength, accuracy, esthetics and longevity.
Reproducible quality is of the utmost importance.
So after hearing stories of ‘back in the day”, because he is from ‘ back in the day’. We are on to how esthetic restorations have evolved to pressed ceramics and now to CAD/CAM.
Lets go CAD/CAM !
This is a modality in our profession that has made leaps and bounds in growth over the last 10 years. There is no going back. And why would we do that ? Doesn’t matter if you are using an IOS or taking analog impressions in your office, in the Lab we are primarily scanning, milling and hand finishing. Yes with the custom, feldspatic layering on request.
Point of view.
The cost of alloys went way up a year or so ago. Patients are expecting metal free. And we all have our high demands and expectations as well. Zirconia and eMax are now our go to as a framework for all ceramic restorations. Lithium disilicate and zirconia come in blocks and pucks with gradient translucency and shade. The lithium disilicate can even have zirconia reinforced in it. They are highly esthetic, strong and precise down to single micron accuracy.
We have the ability to still achieve realistic tooth anatomy and morphology with milled restorations thanks to the design software available. If you have kids that are gamers or you watch a lot of action movies, you know just how creative computer software has become.
The image above is an example of a cut back milled framework in CAD. As much or as little morphology can be created leaving room for specific characteristics and translucency.
We can have the best of both worlds !
We have the benefit of combining science and technology
with art to create
beautiful authenticity.
Written by Roberta Bertram CDA
Reviewed by John Zahel RDT