Your descriptions appear that you felt pain when the dentist did selective grinding of a tooth which was crowned and root canaled. In general, it's true that you should not feel any pain. However, all pains are real.The possibility of your pain source may be vibration of slow speed handpiece or high speed handpiece. Slow speed handpiece generates more vibration than high pseed handpiece does.The offending tooth is probably very sensitive to pressure or mobile.If there is no jaw bone pathology associated with the tooth, the common source of pain is occlusal trauma.Less frequently, it may be referred pain from masticatory musculature. Seeing an occlusionist or prosthodontist is advised.
Find out what was used in your root canal. Specifically ask if anything that contained formaldehyde was used and then if Sargenti Paste was used.
There are dentists using this FDA REJECTED root canal material that contains formaldehyde, and sometimes lead and mercury. There are many in the dental field (about 99% of them) who wouldn't use this stuff if they had to. There are cases like mine of immediate problems and some that show up months to years downstream. The name of it is Sargenti Paste aka Sargenti cement, N2, RC2B, RC2W.... Most likely it isn't your problem because so few use it but, like me, you can run into the bad apples. If an endo did your root canal, it is less likely that this was used because the American Dental Association's only approved and accredited endodontic board has a strong position against it. However, I wouldn't assume that every endo wouldn't...there are bad eggs in every bunch.
If that was used, I suggest you find a dental attorney as they dentists know that they are using a material that the FDA has rejected and the dental community is against. Not everyone ends up with significant problems but sinus infections, recurrent infections are some of the minor issues. You can search for more about Sargenti Paste in google. There was nothing out there when I was injured. I've made sure that changed so others don't end up like me. ALWAYS ASK IF FORMALDEHYDE IS BEING USED...even if you've gone to the same dentist for decades....you'd be surprised about the dentists use it...in secrecy of course.