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…
Wouldn’t that also then happen with something dry and/or salty, like pretzels?
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.
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.