I am having some tooth troubles from my childhood.
The hot and cold issue
Just blowing my mind off.

It sounds like you are suffering from sensitive teeth. It can be very difficult and painful to eat things like ice ream and cold drinks. There are toothpastes like sensodyne that do claim to help this condition and also a word with our hygienist or dentist might give you some clue as to why you are having this trouble. It would be a good idea to have a consultation so that you know what you are dealing with. It does seem that some people just do have sensitive teeth and that nothing really is wrong or can be done. I hope you find something though!

the most powerful exercise for the dental is the chew the food longly. Other wise chew the chewing gum.it gives our teeth good exercise.

I am not sure that the teeth need exercise but chewing gum is a good idea as it cleans the teeth although it should due realised that it should be sugar free gum that is chewed as the teeth definitely do not need sugar! Chewing food well is more to aid digestion than it is for any other purpose as the digestive system can deal better with smaller chunks of food.