Did the dentist shave/file too closely as to expose a nerve?

I don’t think he exposed a nerve preparing the tooth. When a nerve is exposed, you tend to feel it immediately, even when you‘re numb. A certain percentage of teeth that have crowns will eventually need root canal therapy. This may be due to the pulp being traumatized by crown preparation or the fact that crowns are often done on teeth that are fractured or have large fillings. Both of these conditions would increase the risk of bacteria infecting the pulp.

We never know when preparing a tooth how the nerve will be affected. Most times there isn't an issue but every once in awhile the nerve is traumatized by the drill resulting in the need for a root canal. The dentist didn't do anything wrong, it is just how the tooth responded.

Hello! That’s not fault of the dentist… normally when we do the preparation (shave) of the tooth it happened. Sometimes is the nerve is not affected we decided don’t do root canal but in case your tooth don’t support the preparation have to do root canal.  Good luck!

I understand your concern and frustration, but the answer is complicated. He may have gotten too close, but to make a crown, he does have to remove a certain amount of tooth structure and the process is irritating to the tooth. Additionally the germs that caused all the damage to your tooth to where you needed a crown are still lodged inside the tooth. Impossible to get them all out. Some of the germs can be quite aggressive and this one appears to have overcome your immune system. Whenever a dentist goes into a tooth, there is a risk of "complications" similar to what you are experiencing. That is why it is best to care for your teeth and prevent as much dental care as possible.