Pressure sensitive tooth

I had a white composite filling on my second molar tooth at the bottom right side. I never had any tooth sensitivity when this was placed. Two months ago, the filling fell out. The dentist replaced it with the same type of composite material. Since then, I had sensitivity to hot and cold and pain whenever I bite down on anything hard and crunchy. The dentist drilled a small trench down the middle of the tooth. He said this would release the pressure applied by the filling. He then refilled the tooth little by little. If this does not work, he told me that he will remove the filling in its entirety and refill the whole tooth. It’s now two weeks since that was done and I still have this pain when biting down. I was wondering if a silver filling would have been better. Has anyone experienced this? Any advice would be great.