i've seen this tread before, and wanted to reply but i never had enough nerve; i just want to throw in my experiences for your consideration.
i used to work in a sheet metal factory. we regularly punched holes and squeezed hardware into millions of sheets of metal of every shape and size you could imagine. during my time there we did some "template" work using sheet acrylic. for a 1" hole we punched a 1.01" hole. acrylic shrinks especially under heat. not as much as zirconia but shrinks nonetheless.
given that knowledge i was able to solve the issues we were having here at the dental lab; our doctors were very unhappy with our PMMA temps; before i arrived they were always tight fitting and had open margins after milling even though the design was spot-on. the trouble was that we were not factoring in the acrylic shrinkage. how we solved the issue was not easy or pretty; because the shrinkage of acryllic is dependent on the cut size and the remaining thickness, we simply threw on a ton of diespacer in the settings for our scanner, loaded the die with clumpy tinactin, and made the margin a lot lower than it should have been (anyone familiar with CAD knows that a LOT lower means about .001mm -.003mm below actual line).
now our temps are hit and miss, as opposed to all misses and no good ones.
let me give you the name of a publication i subscribe to:
Journal of Applied Polymer Science - Wiley Online Library and for good measure a pdf from a material distributor that highlights PMMA:
http://www.steinwall.com/PDF/C-Acrylic.pdf the Origin scanner seems pretty half done. doesnt come with abutment design software? why pay so much for just c+b work if theres no "features" in the software that will let you push the boundary ? everyone and his brother can make crowns. i doubt it would happen but i can see if my boss would permit a "trial period" use of this software to see how else it can be used.
I'll show the pics when I upload them to the server.
est idea on the planet
