We are in the process of eliminating unsupported zirconia in full arch cases. They will all be Zirc over ti bars or we won't warranty them. There are too many negative factors that can cause zirconia fracture from debonding ti bases, to stress fractures from implants that impressioned inaccaurately (yes even with verification jigs...separate discussion about stone jigs vs plastic jigs vs metal jigs, I have a whole list of gripes about accuracy there lol)
Saw a study, I think it was out of tufts a couple months ago with a series of full arch zirc cases and the number 1 failure pattern was a stress fracture in the anterior when using 6+ implants...the supposition is that with so many junctions the chances of inaccuracy multiply and that it was better to space out the implants and use fewer...two of the fractures were between #8 and #9 with an implant site beneath each central....only inaccuracy of impression/scan/model could explain that kind of adjacent stresses. Crazy stuff, but a titanium bar either fits or it doesn't, rather than transmitting stresses long term....why take the chances with such significant cases.
