I have 2 daughters- one is 9 and never had a cavity in her life, and the other is 2 and she starting getting them the minute her teeth came in. They both had exactly the same eating, brushing, nursing, etc habits with similar foods, etc etc. I was told that it could be meds that I took while I was pregnant or the fluoride in water (we moved from rural area so my first daughter did not have fluoride and no cavities.) The fluoride that they add to water, which is supposed to help, is actually a toxic waste product of big corporations. I had NO idea. It can actually INcrease your chances of tooth decay if you get what is called fluorosis.
My daughter is obviously younger than yours, which factored into our decisions to not put her under for fillings, etc. But another thing, aside from the typical dangers, is that anesthetic can cause other problems all on its own. It's a chemical, obviously, so introducing that to the body is going to affect other issues and potentially cause real harm. It has been linked with autoimmune issues (Lupus) and psychiatric issues (Bipolar) and the chances increase with heredity.
We have seen 4 dentists for my younger daughter, and finally found 2 that we really like, both homeopathic. I am happy to get you their names if you are interested in going this route. I will tell you that will 2 relatively inexpensive (but out of pocket) visits, and the purchase of homeopathic products (totaling less than #100 probably) and a water filter for fluoride (a Berkey, about $200) we have actually HEALED my daughter's cavities. She has actually grown NEW enamel which has hardened and the decay has healed.
I hope this helps give you another avenue to consider, since it is painless and trauma-free to the child and requires NO harmful chemicals, no drilling, and ours required no x-rays/radiation at all.
I highly recommend reading Nourishing Traditions by Sally Fallon. It is part cookbook, and part information about why indigenous societies have such healthy bones and teeth and how that is linked with diet. It's a very interesting read and there are some simple ideas for how to get more nutrients for your body from foods you eat every day (nuts, dairy, etc.)
Let me know if you would like to talk further!
M.