So Rob you have a good memory
Not sure this will answer any questions but let me chime in anyhow.
Back in the day any multiple unit splinted restoration was restored at the abutment level not the fixture level. A trans-mucosal abutment was the only way and is what today we call a multi unit abutment. Literally there were no definitive parts for straumann fixtures for a bunch of years because 1, the lit all said things needed to be done a certain way, and 2, it sold more parts
Yeah my opinion
Fast forward lots of years, back in the day NT trading didn't even have non eng ti bases, they had a really horrid MUA path called Two connect and it followed the old lit about only restoring to the abutment level. Heck probably had FDA crap to get around too???
All of the prefab parts that FDA was cracking down on even to this day is regulated and I am sure Keith from Dess USA will chime in if he is still on this site essentially was some of the first in the states that had a clean path to restore splinted restorations.
Today the milling centers are still playing fast and loose with fixtures, many may be milling more interfaces than they should and thats not for me to spill the beans on.
One of the first milling center to offer a NON ENG custom abutments to my knowledge was TRU Abutment and I can attest they are great. Are they compliant, again thats for you to ask them.
Remember anything touching a fixture that you buy that has compliance will always have compliance as long as you run a clean biz have good GMP's in place and track your lots. For years we would take abutments put them on a mini lathe and round over or cut off parts in a very clean precise way, The vast majority of internal hex fixtures will still have a projection ( I call it a chimney) in contact with the morse or tapered wall of the fixture. I have many many cases done this way it works plain and simple.
Regulations, piggybacking off of others 510k is essentially what us labs do daily, its still on your to keep good records but in todays market where you can get a bitchen custom abutment from an approved milling center for less than 100 bucks makes it seem so silly to even consider milling in house.
Even premils which we do mill in my lab are ONLY done when someone in my lab screws up or we need to rush out a special favor case.