I can give you both sides of the debate.
My dd had serious decay starting at 3. The dentist we went to at the time felt since she was not in any pain, we could take a wait and see attitude. We treated her with topical flouride nightly, cut out sweets(which was not hard too do since we had never had too many in the home anyway)
She was fine. Her teeth never decayed any worse, and her babyteeth all came out on schedule, and her adult teeth were fine.
So..
My youngest son,5, started showing the same signs of decay as my dd. I figured we would take the same approach. We practice very good oral hygiene, he flosses, rinses and brushes after every meal religiously.
In spite of this, he developed severe decay, and recently began getting headaches and a toothache on one side of his mouth.
He went today for his checkup, and the side where he was getting headaches and pain is severely decayed and now has to be extracted. Fortunately, I have a very gentle dentist who also does not believe in general anesthesia for surgery, and will allow me to remain with him.
He said if we had allowed it to go, he could quite possible have gotten a bacterial infection in his sinus cavity. This could be very serious, even fatal.
Knowing this now, I know we were just fortunate with our dd.
I urge you to search high and low for a supportive dentist, it took me a very long time to find the one I have now. But I also urge you to not take the sit back and relax approach. I do not know what I would have done if my son had gotten sick from this. As of now, just knowing it could have happened, I have a lot of guilt.
Good luck to you.