I've asked my dentist about this but they seem to just blow it off or think I'm exaggerating.
Whenever I touch or see some plastic things (Lego bricks, plastic drinking cups, etc.), my bottom teeth start to hurt towards the roots. It's always been this way, and the exact same thing happens with my mom with the same kinds of plastic objects. Not all plastics things do it, but it's especially bad with little things and plastic toys.
Does anyone have any idea what could be causing this? I haven't been able to find anything about it. My mom and I speculate that it could be some sort of chemical used in making those specific kinds of plastics, but we're shooting in the dark.
The liquid in the plastic cup may contribute to your pain or sensitivity also. If you have cracked tooth or cracked/chipped fillings, the liquid which is cold and sweet can penetrate through that area to the nerve inside your teeth. You can try to use straw to see if that help. The dentist will give you a better diagnosis.