Is a sensitivity to sugar a sign of a cavity? i've noticed that one of my teeth recently feels really weird when i bite into something very sugary (candy, cupcake frosting, etc.). could this be a sign of a cavity?

Yes, : Yes, it can indicate decay. It can also indicate a loose filling, or a cracked filling. Since you just started feeling the sensitivity, it could be something very simple to correct, like a small filling. Best bet is to have it evaluated by your dentist.

Usually : Usually it is a sign of a cavity or a cracked filling.. I would recommend seeing your dentist and having exam and an xray.

What : What you are feeling is called an "osmotic change" due to saliva not having as much water when very sugary. Fluid concentration is shifted out of the tooth, and the sensation is exaggerated with cavities, broken fillings or broken teeth. Sometimes the solution is very simple, but may be complicated, so a visit to the dentist is a good idea.