I have a great insurance that cover like 80% of root canals and crowns, which is a blessing. And I feel your pain, I have had 2 root canals in my life and the process is scary and awful. I try to go to the dentist every 6 months, me old dentist office closed without notice, send my records to another one that I went once and never again. They did X-rays and pretty much told me that the other office had done everything wrong and that I need it: 1-new root canal on and already root canal, 1-new crown on the other root canal because it was done incorrectly, and basically the rest of my molars (all of them) need it fillings. They "Checked' and said that because the crown that need ti replacement was done withing 1 year of the transfer it was under warranty and "I" had no expense for it, so I said fine redo it, of course they charged the insurance anyways. Root canal and fillings I forgo, and changed dentist, the new ones checked and showed me the "New Crown that was missing a Piece" so they had to redo it, made me so mad. The root canal is fine and DO NOT need to redo, and I only had 3 fillings not all the teeth. Dentist offices like your $$ and try to scam you.
Now my daughter had 1 root canal done and her crown fell down the other day, she got a temporary one and that one fell down too, I guess they did not use an strong enough cement.
Many years ago I had a Dentist that wanted us to pay the difference between what they billed to the insurance and what the Insurance paid them, even though that is not supposed to be like that.