My sister had the SAME THING with her 3 year old daughter, and in less than six months has TOTALLY stopped the decay and prevented the need for ANY type of surgery or invasive treatment. And get this, she didn't even do everything that Rami Nagel recommends! If she would have, there's no doubt that her daughter's teeth would have totally healed and made new enamel.
(She had this confirmed with X-rays...the periodontal tooth decay was totally halted!).
The human body (especially that of children) is HARD WIRED to heal and restore itself. When we break a bone, the body makes more enamel to heal the bone...so if it'll do it for bones, it WILL do it for teeth. "They" have convinced us and taught us otherwise, but they are WRONG!
1st thing you do, is stop brushing her teeth with any type of toothpaste that contains GLYCERINE. Glycerine puts a thick coating on the teeth that prevents the bacteria from getting out, and the healing minerals in the saliva from getting it. You'll probably have to switch to some type of natural 'tooth powder' (my sister did), because she searched through ALL the natural toothpastes and couldn't find ANY without glycerine. (I assume you know that fluoride is also very bad for teeth and health).
Then just follow all the diet/supplement recommendations in the link above (and email if you need sources for the supplements...high grade fish oil, butter oil and echinacea) and you'll turn it all around in a matter of weeks! (The quality/brand of the fish oil & butter oil are VERY important - there's only three fish oils on the market that 'pass the test'...the best is here (and you can get the high-quality butter oil here, too):
The absolute WORST THING you can do for your child's health (and for her incoming adult teeth) is have root canals. Please don't subject your child to that - it can and will destroy her health and teeth.
Don't believe what they are telling you...they don't know how to heal, they only know what they've been trained to know! You can easily (and SAFELY) restore your daughter's teeth without all the risks and dangers of surgery & root canals. I am absolutely, positively SURE of it!
Healthiest of blessings -