Your question although a good one for you is missing information to possible give you a better reply. Not all orthodontics expand people jaws. If they do there is a good reason why. I am not sure if you are a minor, but if you are think of it this way. Your parents are not going to want to pay for treatment that is not needed. However it does not matter weather you are a adult or a minor ask your orthodontics these questions. If what they tell you is not enough let them know. Make the explain to you until you fully understand the whats and whys of your treatment.