They did a checkup and an xray, and a few days after the xray they phoned to tell me that I needed a filling. (Bummer, thought I, I nearly made it to 30 without needing any fillings.)
So I went in for the filling, and when I was on the chair with my mouth propped open they asked if I wanted the NHS filling (mercury filling, lots of drilling under anaesthetic, painful, unsightly grey lump in the tooth, cost = £45) or the private filling (non-mercury, very little drilling, painless, invisible, cost = £70). I opted for the invisible/painless option, which took about 5 seconds of drilling and 2 seconds of holding some kind of instrument against my tooth (I'd been told to close my eyes so I have no idea what).
After that was done, the dentist showed me the xray and said that there was another 'shadow' visible on the xray and I might need another filling. "It's only a very slight shadow, you probably won't even be able to see it," they told me, pointing at a completely blank bit of xray. They were right. They took another xray from a different angle and said they'd phone me back if anything showed up.
Surprise surprise, they reckon I need to pay them another £70. This feels like a phenomenal ripoff; for all I know, they are inventing these 'fillings' out of thin air. They can't provide any evidence except a blank space on an xray where they claim to be able to see something. Now obviously being able to spot things that mere mortals wouldn't spot on a postage-stamp-sized xray is the sort of thing that one might get from 7+ years of training to be a dentist. But they're certainly not inspiring me with confidence.
The 'drilling' is apparently only a tiny bit (no pun intended) on the surface of the tooth, so the 'filling' must only be the merest cat's whisker of the dental equivalent of polyfilla. I've always taken the view that teeth are worth protecting; but, if I was being completely cynical, I would point out that it is hardly rocket science to work out that people of my age a) were probably brought up to take this view of toothcare, b) probably feel slightly guilty about not brushing seven times a day and not using all the available tooth-cleaning technology, so can probably be persuaded that the fault is theirs, and c) have a reasonable amount of disposable cash.
I don't think there's any way I can get a second opinion without paying outrageous amounts of cash to some other private dentist; there simply are no NHS dentists in the area (and of course you still have to pay for checkups even on the NHS). Of course, they know that, too.
But if I just told them I didn't want to have it done, then a) they'd kick me off their books (they'll only take NHS patients in the first place if their teeth are okay) and b) I'd feel as though my teeth were a ticking time bomb in my mouth. Maybe £140 isn't too much to pay for peace of mind. But it still leaves me feeling as though my mouth is full of snake-oil.