A few of my problematic teeth (with fillings/ageing fillings) hurts particularly bad when I have a cold, upper and lower jaws. But a day after the cold, my teeth are normal again. What does cold do to affect these unbearable pains?

Is it bad to get 2D panorama X-Ray? How much radiation does it gives? And is it really necessary for non-orthodontic cases? As individual tooth x-ray shows better clarity of a problem tooth rather than panorama isn't it?