So on Thursday I had the second dental impression referred to in the previous entry
. This was a little more involved than I expected.
The end result of the implant process has been that there's a convenient metal adapter in my jaw, with a threaded screw hole in the middle, but also, around that, a shallower hexagonal socket that the final abutment will key into so it doesn't turn. In order to make the abutment and crown align properly with my other teeth, the lab that will make them needs an extremely precise reading of the orientation of that hexagon.
The way they got that is kind of interesting. The rough impression I had a couple of weeks ago was just to make a custom tray for this second impression, which used a much more rigid-setting, extremely vile-tasting purple material. But before taking it, the dentist unscrewed the simple healing cap that's been hand-screwed into my implant and replaced it with something called an "impression coping". This was a piece of metal with a hexagonal base that keyed into the implant, and was held in with a separate screw sort of like the final abutment will be. But instead of the support for a crown, the top of it was a vertical post with two weird bow-tie-shaped projections sticking out to the sides. The central screw holding it in was a long thing that stuck out far enough that I couldn't bite down fully.
They put in the impression coping, took an X-ray to make sure it was securely seated in there, and poked a hole in the custom goop tray so that the screw could stick right out through it. Then my dentist jammed the tray down over that with the impression goop inside, told me to bite down on his fingers holding the tray in place, and stood there for five minutes humming along with the Sixties pop on the satellite radio and pretending not to be uncomfortable with me continuously biting him.
When the impression was almost fully set, he unscrewed the long screw, then lifted the tray of hardened material off my jaw so that the coping came right along with it, with the projections at the top stuck in the impression material. The end result was an inverse image of my lower jaw with the impression coping sticking out of it, its hexagonal base registering the angular position of the hexagonal socket in my jaw.
Anyway, I thought it was interesting. The healing cap's back in now; I think the next step is to CNC-mill the metal abutment, and my next visit is to check the fit of the abutment before the crown on top gets made.