You may want to consider clipping the top and bottom teeth if you are going to feed live. It is not that hard to do (wearing a kevlar glove gives confidence) and is not that dramatic to the rat. If the snake does not eat it, the teeth grow back.
Before anyone starts yelling CRUELITY, if you are careful it is not big of a deal.
Besides, it's a food item. Better the rat than a bite to the snake's head or eye.