T
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My experience with cast PFMs is that about 75% end up with recession, many with discoloration of the root, gingiva, tooth, or any combination. The oxides necessary to bond porcelain is a major culprit, along with corrosion and the toxic nature of "some" of the components. The latter point was published in 1997 in Germany.
I have electron micro photos of the oxide layer on hi noble and NP. The Au metal has a layer of 1 micron, while the NP has 100 microns.
You might not have had complaints about tissue and NP, and clearly not everyone reacts or reacts the same. But I can promise you that there are reactions, even with other metals. I saw it for about 20 years with a variety. That is why periodontists tell GPs to stey supra ging with cast PFMs.
That's why Captek is the only true PFM crown.....lol
Seriously though, I'm wondering if anyone has ever taken an electron microscope and looked at the oxide layer between the opaque and metal (curious to know if it's a measurable amount). If it was, it would make me wonder about fractures on traditional cast PFM's.
I posted photos I obtained in an article I wrote for the JDT. It showed the oxide layer on high yellow noble to be at 1 micron, while low gold was 100 microns. In the photos the oxide filaments were better organized and thicker for the high noble and appeared much more fragile for the low noble. This might be only a characteristic of the metal brand shown, but research at Boston U indicated that the porcelain bond strength of yellow high noble and Captek were about twice that of low noble and NP metals.
Wow, now it makes one wonder how many Non-Precious (car bumper) metal crowns fractured due to the oxide space under the opaque layer.....scary
I use HN. W, from Ivoclar 54% au. Also I use Brite Gold 96.3% au (BG XH 88.9%for bridges) as a replacement to captec. Glass bead the inside and you cant tell the difference between the two.
One thing I dont like is to use an alloy like some high PD types that require you to sand blast after oxidation.
Higher prices isnt really a factor for me because its been an incentive for Drs to use all ceramic.
Also I love the return on the scrap!!!!
Thanks Ill ck that out because I see it has only 9.2 ag.I agree with everything you mentioned on the alloys! One thing I can recommend to you is ask your Ivoclar rep about the HN Evolution Lite alloy. This is a 40% gold (high noble white color) that works just like the "W" and costs over $100 less per ounce! The Evolution Lite also has a lower density, so you will get an extra coping (or two) on every ounce!!!
Thanks Ill ck that out because I see it has only 9.2 ag.
Also I can use the POM kit on that but not on W. I bought that kit when it first came out but they dont have a incisal porc to add on after its pressed
All they have is denten shades to match the ingots.
I used it once and it worked ok but I can build quicker. I thought I might use it to press on to some larger bridge frames or maryland bridges or implants that require alot of tissue coverage, but without enamel add on porc I guess it will collect dust.
Yep I use InLine, Do you know if they are going to come up with an enamal porcelin to layer onto POM????Yeah, the 9.2% Silver has (and will have no) effect on anything you do in the lab. The CTE on the Evo Lite, like you said allows for the PoM system. The PoM delivers nice results for it just being a full press, stain & glaze. I like the option of pressing 360 shoulders super easily. Do you use the conventional InLine porcelain for layering?
Yep I use InLine, Do you know if they are going to come up with an enamal porcelin to layer onto POM????
Six, FYI, since this post I switched to Evolution Lite from W. I have used several oz's of it and am very satisfied. Its harder so I dont have to beef up my connections quite as much on long span bridges and the margins dont elongate during final finishing like they did with W. The oxides are not as light as with W but they are still acceptable.One thing I can recommend to you is ask your Ivoclar rep about the HN Evolution Lite alloy. This is a 40% gold (high noble white color) that works just like the "W" and costs over $100 less per ounce! The Evolution Lite also has a lower density, so you will get an extra coping (or two) on every ounce!!!