The next weakest point is going to fail.
that is precisely the problem, and in fact, the entire point.
processed acrylic is really really really really weak.
not a single person would make a titanium structure bigger than a bar - an all-on-4 for example. the results would prove disastrous. titanium teeth would be ugly, weigh a lot, and crush the rest of the mouth to dust.
you want a semi rigid material for all on 4, that is aesthetic, doesnt weigh a ton, and can be layered to. zirconia is what many people go to, however under the strength tests we've performed, an AO4 out of zirconia would outlive the patient. our testing indicated usual mastication force would need to surpass 800Kg to begin to strain it. at least with polishing it can be easy on the opposing.
this is a ludicrous amount of force, however. anyone undergoing that amount of force will see the zirc hold up but it would immediately de-integrate the implants. all of them. at once. without resistance. its too rigid. it absorbs force not at all.
you want a less stable superstructure for all on 4 so that the implants will survive. you want the implants to survive so you can make the prosthetic again, and not cost the patient another year of healing and the cost of 4 more implants. less stable superstructures is safer than strong superstructures.
so the question is now how to get rid of processed acrylic and replace that with a stronger, more shock absorbant material; irrespective of the choice to put it over a bar or use it as a conversion.
resin is your friend. resin is the future.
now, some folks want to get there slowly, and thats acceptable. Trinia is there to help you go slowly. its an inesthetic material that tastes terrible, is fibrous, and isnt repairable. however its less stable than titanium so its uses are already outlined. as stated a few posts ago theres also PEEK for people who are already a bit late to the game.
in that future expect a resin material that has a huge elastic property with a characteristic of being rigid with increasing thickness. i've got a few different kinds of this to crush and figure out the better of the batch, but i am pretty confident to say i know what is the new cream of wheat for 2018. remains to be seen yet though, how doctors and prosthos and denturists respond to the useage of these materials. without a good adoption rate, i might as well be sitting on my hands. zirconia was adopted quickly because of how easy it was to get into; cadcam companies far and wide bought into the development and thats what made the roland machines so hugely successful. what i have, it might be difficult to understand how it processes - from acrylic to cadcam resins. its a bit of a bitter pill to swallow to say you relinquish control of the product to a machine. so i know adoption might be more tricky when explaining its mechanics to those less of the inclination towards the science of materials.
its easy to push juvora peek and say hey here look at this new cool framework ((just please don't think critically about how you add to it, repair it, or modify it once its made))
those who haven't got that kind of inclination, don't know to ask about those kinds of things. so after a hundred cases and 99 failures, they look for something else and probably circle back to CoCr or Ti frames until they get the bad taste of peek out of their mouths.
its not easy to come up with good reasons to buy into new materials until you recognize the shortcomings of the old materials, and if you only ever want to make ti bars and plastic dentures, that's your prerogative. but sooner or later all your colleagues will be asking about your experiences with new kinds of resin and new cadcam machines, and you might feel a bit out of the loop if you still have your blinders on.
i get where you are coming from; a year ago if you asked me what was the best way to make a denture over implants i'd have said a ti bar and a piece of plastic you can lock in with a pin. since then however, as The Dude would say "New Sh1t has come to light, man" and it requires to rethink the process from the ground up. assume nothing. take no proven statistic for granted. question what you "know" and you end up in a different place at the end.
