To the OPs original question: how do you test accurate fit? It seems no one has an answer other than to see if the margins are closed, which doesnt fulfill the requirement of testing 'fit' only marginal integrity. Unless someone has x ray eyes, or completely trusts a machine, theres no way to see how the intaglio of the crown touches the die, unless you have an indicator. Margins are crazy and sharp and uneven and scanners and mills cant always capture that. At least thats my experience, but everyone has different standards and practices.
I use generic foot powder spray at $8/can and touch any high spots with a two striper. It takes less than 30 seconds. Maybe thats too much time to spend on a crown for some. You can also have your Dr send you the radiograph when its cemented, the newer digital tech is brutally honest.
the problem is, no one talks clinical significance.
of course the intaglio surface isnt going to be exact, nor should it be for proper fit. and since every prep design is significantly different from the previous, each "fit" should be treated individually....and more importantly with the cements on the market nowadays, what type of 'improper' fit will be clinically significant?
as in: lets say a margin is slightly open, but the cementation process is completed properly and the gap is filled and set as it should be....lets also say margin integrity is as accurate as we can get on a subsequent crown, and cementation is done properly. both cases most likely will have no clinical significance for that precise or slightly open margin. why? because generally, the cements used block only so much of bacteria. whether the margin is sealed with the crown or cement, the micron thickness of bacteria either can or cannot penetrate the seal. this goes for conventional crowns, digital, composite, etc.
Really I dont see why its such a big deal to spritz a crown and see how it touches the die.. seems lazy maybe? I bet you would be surprised at what you see.
