Hi
How do u know they are dead teeth? And if u know why haven't u go them treated?
Next Steps
So first visit a dentist and find out if the tooth/teeth can be saved. Swelling on hot food or as per you if it's a dead tooth, needs to be treated with root canal. A good X-ray will determine the cause of the same. Whether the problem is in gums or tooth/teeth.
Health Tips
Get it treated before u have bigger swelling or the tooth breaks. You are young and should try to save the tooth as much as possible. Take care.