I think you do need 1100mpa as the periodontal ligaments are not there when doing full arch implant cases . Thats why most people use Zi for full arches as they have seen to many chip as Vmk,s whats the average compressive strength or the porcelain on a vmk at the correct thickness and support? its about 650mpa. Patrick you should know this because you guys at Ivoclar talk about how much stronger something is once you bond it like with emax.As far as the 2 pontic thing goes i understand there is a certain amount of a55 covering going on but im pretty sure Zirkonzahn doesnt feel the need to do so and there prettau 2 dispersive transitional colour and transitional transluscency blocks have been around for a while now .
Absolutely correct, under compressive forces glass is very strong. That's why you can take a flat piece of window glass and lay it on a flat hard surface and roll a car over it without it breaking. But once you put a flaw in the surface it is laying on we are now looking at a shear force and it will break at that flaw with very little effort.
Lets take a perfect scenario and say that the substructure of a restoration was designed perfectly, no flaws. And the technician did everything perfectly with layering and firing. And the dentist cemented that restoration perfectly. Centric is perfect. When the patient clenches in centric all the ceramic is under compressive forces (this is where your 650MPa compressive value comes in) and nothing is damaged. Once that patient goes into excursive movements, compression is out the door and now we are talking shear and the layering ceramic is again only in that 90-110MPa. And if all excursive movements were not worked out to disperse that load (or take that load completely off it) the restoration chips or breaks.
However, when we discuss high strength ceramics that are monolithic (whether lithium disilicate or zirconia),we do not see this. In fact I have a study showing monolithic lithium disilicate taking 3 times the newtons (same measurement as MPa) of a layered zirconia restoration (layered zirconia-350N, lithium disilicate-over 1000N, with 10 times the cycles).
Given this information, I would have no problem using or recommending PRIME in these situations.
As far as the two pontic thing, I believe this is an FDA thing (now I can't say why all companies recommendations are not that way). I say this because, this is the same recommendation we give for all our high strength zirconias, and we can't even give that recommendation in Canada. Because of Health Canada we can only recommend up to 6 unit restorations with maximum two pontics in a row. In fact if you change the language/country on the ZZ website from English(US) to English(CA),the maximum recommended bridge length goes from 16 to 6 (yet they still show and talk about the "Prettau Full Arch Bridge" on that page).
