How do I test Zirconia puck quality?

[alandang]

I am running a startup lab and we have been trying a variety of zirconia brands. I pretty much only use brands that have all vita shades and have 30mm in stock. That being said I realize that not all zirconia are made the same.
What I understand so far:
Some mPA ratings are skewed using biaxial strength test with a flathead punch and surface treatments done to the puck which in turn gives it a higher strength reading. lly strength testing is done by exerting a downward force on the midpoint of a zirconia bar, the 3-point flexural test

Zirconia pucks are mixed with yttria which gives it the translucent look but as a consequence lowers the overall mPA of the puck. Manufactures have to figure out a good ratio that solves the problem of strength and aesthetics. Some manufacturers utilize clever processing methods in order to make the elements in their pucks finer/smaller before pressing to increase density which increases strength.

If I got any of these wrong please feel free to correct me.

Knowing this information is great but… when I as a customer receive new pucks from new brands how do I test what the actual mPA is? And do y’all know any methods of testing zirconia which indicate good/bad quality manufacturing. I have heard of putting zirconia in a glass of water, if it floats it means it’s of bad quality. But is their any methods of testing where I can see real concrete numbers and compare them to brands I know are reputable?

 

[CoolHandLuke]

Zirconia pucks are mixed with yttria which gives it the translucent look but as a consequence lowers the overall mPA of the puck. Manufactures have to figure out a good ratio that solves the problem of strength and aesthetics. Some manufacturers utilize clever processing methods in order to make the elements in their pucks finer/smaller before pressing to increase density which increases strength.

the entire field of X ray crystallography would like to tell you this is incorrect.

optical translucency/transparency is derived from how closely the zirconia is to a Cubic lattice, which means the arrangement of atoms or molecules in the crystal structure must be arranged as close to cubic form as possible to acheive translucency or transparency. we did have a zirconia that claimed to be a cubic product, but after learning this much about x ray crystallography i can confidently say it was a gimmicky name and not an actual cubic state lattice arrangement.

Tetragonal zirconia is close to cubic, but not quite perfect. the atoms form a skewed polygon, so the grade of transparency will come from the angle between the molecules.

yttria is a stabilizing agent, of which only 1 percent by volume is needed to create a zirconia powder that does not ignite or be radioactive at room temperature. zirconia is otherwise unstable. yttria 3% and 5% and 8% are then used as doping agents to secure the zirconia so that shrinkage will be uniform throughout the mass.

now, how you can do your own 3 or 4 point bend test? go to a university material science lab and pay the department head a few grand or have the students perform the bend test as grad work or leveraged against course objectives.

speaking from experience.

 

[Car 54]

As your last sentence says it all IMO, "brands you know are reputable". Use those numbers as a baseline reference, then use those zirconias, handle them correctly, sinter them correctly, build/stain/glaze them correctly. Stay away from the Bed, Bath, Beyond and Zirconia, companies, and you'll sleep well at night.

 

[DreN4do]

I'd suggest either AlienMilling Brand pucks or Ivoclar

 

[JKraver]

Just use something you have heard of with decent reviews. I use ivoclar prime esthetic for pretty much everything and its like 850mpa or something like that and i've never had a posterior bridge break. MPA isn't everything remember that porcelain fused metal bond was only like 80mpa if it was done right. A emax is only 300.

 

[desertfox384]

I do a fair amount of zirconia every year and have very very few break - and some of them are being put past their indications. I mainly use argens ht multilayer, and ultra for frameworks.

 

[grantoz]

i use zirkonzahn and have been happy for years. but my main advice is dont use anything manufactured in china as regulation and consistancy is unreliable i know some on here will say otherwise but thats my opinion.