Sorry to hear of your distress. Sounds like your biggest problem is your own mind. I understand, because I can be the same way about anything medical. My thoughts start running amok with all kinds of fears. As more time goes by, my worries only increase as I start coming up with new things to worry about, even things that are highly unlikely to happen (as you seem to be doing). Eventually I can reach a breaking point where I can't think straight or hardly function. My heart starts beating so fast I think that it will leap out of my chest.
I don't have an easy answer for you but I do know that bringing our minds under control is key, and the key to that is finding the right thoughts to help redirect our minds. I'll share with you a few thoughts and ideas that I try to use to help me.
I remind myself that one way or another, we all have to face difficult, painful things in our lives. We can either face these things with fear or without fear. I choose to do it without fear, as fear makes everything worse. Or at least I try to make that choice, but I know, it's easier said than done, but it's good to at least visualize a goal here.
Sometimes I try to split my mind in two - between a mature, strong, tough, reasoning, logical adult
mind, and a panicked little child mind. I don't deny the existence of the panicked little child mind, I just try to put my adult mind in charge. I want my adult mind to be dominant, to be 80% of my thinking, and keep my child mind in control, with both correction and comfort.
Another approach is to try to just not care. Try to mentally detach yourself from yourself, or at least from your body, as if you were watching someone else, even a stranger, go through this. In other words, try to depersonalize the whole thing. Finding something else, even another problem, another type of problem, to get preoccupied with can help with this one.
Another thing I comfort myself with, is the thought that I live in 2023 with modern dentistry, and not 100, 200, or 300 years ago and before when dentistry was primitive or even non-existent. IOW, we live in the best possible time in all of human history to have dental work. Even today, there are many people who have little to no access to dentistry.
I hope these thoughts might help even a little bit. Anyhow, I hope you are able to settle down and do what you need to do. The IV sedation is wonderful BTW, and I would gladly opt for it when having major work done. I know that the lack of control can be a fearful thing, but in this case, it's better to let the pros be in control while you take a nap - just like we do when flying.
I am actually having some dental pain going on right now and I have an appointment in a couple of hours for an assessment. I'm very nervous that there's a major problem that will require major work. So when I come back on in a panic talking about how I need to have a root canal and extraction and whatever else, feel free to throw all of my words right back at me.