I have oft used the phrase “so sweet it makes my teeth hurt,” but now that I am of an age and have some sensitive teeth, things that are very sweet really DO make my teeth hurt!
I can understand why heat or cold might cause dental pain, but why sweetness? What’s the physiology behind that?
Incidentally, the couple of teeth that hurt when I eat something really sweet are not the same ones that hurt when I eat something cold.
I experience this as well. Especially with sticky candy like caramel or nougat. I don’t eat those anymore. <shudder>
ETA: So while I don’t know the answer, I’m eagerly awaiting the response of somebody who does. 
I have always assumed it’s an osmosis thing, if you have strong sugar solution in contact with a cavity on your tooth then it will draw water out from the interior of your tooth, stimulating the nerve and causing pain. But I have no actual evidence to back that up, and on thinking about it, salt ought to have the same effect but it doesn’t. Ah well…
[QUOTE=Colophon]
I have always assumed it’s an osmosis thing, if you have strong sugar solution in contact with a cavity on your tooth then it will draw water out from the interior of your tooth, stimulating the nerve and causing pain. But I have no actual evidence to back that up, and on thinking about it, salt ought to have the same effect but it doesn’t. Ah well…
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Wouldn’t that also then happen with something dry and/or salty, like pretzels?
[QUOTE=Joey P]
Wouldn’t that also then happen with something dry and/or salty, like pretzels?
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Actually I have noticed that - when I had a filling come loose and expose a cavity, eating dry crackers etc also made the tooth hurt.
[QUOTE=I’m Pavlov. Ring a bell?]
I think germs in the mouth instantly turn it into acid.
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Oral bacteria do synthesize carbohydrates into acid, but if acid were a factor, then sucking a lemon would also make my teeth hurt. Lemons don’t have that effect on me.