I had a root canal and was terrified, it turned out to be great as the nerves in the tooth were already dead. A dog has a GA and will feel nothing, a bit sore afterwards perhaps. I have seen lots of dogs have dentistry, usually extractions and they are fine. Hope Homer will be home soon and you can relax that it is all over. I found it so different when it was my dog undergoing an op, a nervous wreck, so I understand how you must be feeling.