The process is fairly simple: basically they fill a plastic dental plate with pink goo, whack it on your teeth, and hold it there until the pink goo sets. It's not painful, and the goo is mostly tasteless, but the fact remains that you're sitting there with your mouth wide open and stuffed with something that feels like rather vile-tasting chewing-gum while the dentist leans heavily on your palate.
(Actually, it's not quite like chewing-gum. The consistency of this stuff, when it goes in your mouth, is almost exactly the consistency that Blu-Tak goes when you chew it. DON'T ASK. It sets harder than even the Blu-Tak that you find in the corner of your desk drawer when you leave a job.)
"What's that stuff made of?" I asked, inbetween impressions. (Obviously. If I'd asked while I had the thing in my mouth, it would have come out as "Och ha ush aygov?")
"I'll tell you afterwards," he said, smirking. ... Then he relented. "Nah, okay. It's made of seaweed."
"Oh! Cool," I said. I wondered if he expected more of a reaction.
"Well, you eat it in Chinese restaurants, don't you," said the cheerful dental nurse.
"Yeah, exactly," I said, thinking, actually, that's cabbage, but never mind.
"That's cabbage," said the dentist. The nurse looked amazed.
"You mean it's not real seaweed?"
"Nope. It's cabbage. Check it with [someone] if you don't believe me," he said, and then explained to me that the chap he'd named was one of the other dentists, whose father owned a Chinese restaurant.
There was a long silence which, my mouth being full of dental equipment, I was unable to interrupt. Finally the silence was broken by the dental nurse.
"I always thought it was real seaweed," she said, in aggrieved tones. The dentist laughed at her, and I tried to laugh with him while not seeming to laugh at her, a conceptual comedic contortion which nearly made me sprain a tooth.
In addition to the impressions, they took photos of my teeth. I bared my teeth hungrily at the shiny digital camera (a common reaction) but the only snapping was that of whatever you call the camera's digital analogy (if that isn't too much of an oxymoron) for a shutter. As well as my unaided grimace, they took several photos of my teeth being forcibly bared by a plastic mouth-opening device. Not quite Clockwork Orange stuff, but still a bit gruesome. They also held up lots of FAKE PLASTIC TEETH next to my teeth to try to work out what colour the veneer will have to be, like the toothy equivalent of a Dulux colour-charts. I'll have magnolia with a hint of coffee-stain, please.
As the dentist was writing up his notes at the end, I asked if I could have copies of the photos -- "so I can do a 'before and after' thing on my website." His turn to laugh at me, now, while the nurse looked baffled. "Yeah, okay, it's a bit sad, isn't it," I said. "No, not at all," I expected him to say. "Yeah," he said, grinning.
(He's agreed to give me the photos, though. One of them should be just a full-frame photo of my mouth with a long row of FAKE PLASTIC TEETH underneath it. It would be weird to have that as an LJ icon, right?)