Why is it that my teeth are sensitive to chocolate?

Cavities: Your teeth are sensitive to the sugar in the chocolate suggesting that you may have cavities or leaking old filling, in any case you need to see the dentist for an examination and to get nee flings.

Sugar possibly: You may have sensitivity to sugar. This could be a sign of cavities or gum recession. Recession would leave the roots of the teeth exposed. I recommend seeing your dentist for further evaluation.

Several causes: This would tend to indicate that you have cavities, defective margins around your fillings, cracks in the teeth, exposed root surfaces, or erosions. You may have more than one of these conditions. See your dentist in order to determine what dental treatment, if any is necessary to make you more comfortable and prevent more serious problems.