LizGood morning, Liz.
The symbolism of teeth in dreams can be very confusing. Let's have a look at the surrounding context of your dream.
In very general terms, you had thought something was permanent (the dental work) when in fact it was not. The people you trusted to take care of the problem took a great deal longer than necessary, and didn't seem suited to the job. However, in the end, the problem is fixed, and you berate the person responsible for doing a poor job in the first place.
When laid out in this fashion, it becomes a little easier to see that those terms could describe a great many things in one's life. Now we need to start adding in context clues.
The people you hire to repair your crowns and fillings are Penn and Teller. Their brand of show is more comedy than magic, and often based upon pain. However, in the end no one is really hurt. Entrusting people like this with a personal problem could be interesting, to say the least - there would always be, until the very last minute, doubt over whether they would help or harm you.
You go off on several tangents, but end up back at the dentist's office. It seems that this is a message that, whatever the real problem is, it's going to haunt you until you deal with it once and for all.
Your real dentist represents the originator of the problem, the one who was supposed to take care of it but didn't. This could point to an ex-husband, an old way of thinking, etc. It's something or someone that you no longer trust.
Which brings us back to Penn and Teller, your "new dentists." Given the paragraph above, this seems to be someone or something that you aren't sure you can trust, but will get the job done even if the methods are unorthodox.
What all of this means, then, hinges upon what your broken teeth represent. What normally comes from a person's mouth is words. Given the context of your dream, it seems to me that the teeth represent a broken promise. Whether you made the promise is irrelevant - you feel responsible for it.