[AKDENTAL]

My husband has many amalgam fillings. One of his molars hurts when he brushes his teeth. It has a large amalgam filling and it shows on the side of the tooth. I'm not sure if it's always like that or the tooth cracked and the filling is showing. The filling is very old. He got it during his teen years. I'm afraid when he get it replaced, it will damage the nerve. What's the best way to treat it? Can the dentist just put bonding on the outside w/o replacing the old filling if there's a crack in the old one? Is there drilling involved when replacing the filling? Thank you very much for your help and info!