I am sure you probably already did something for your son's teeth by now. As I am only just now finding your post a year later. But, if he still has trouble, or just for future reference, check out the book, "Cure Tooth Decay" by Ramiel Nagel. I recently purchased that book because my 7 year old's new permanent teeth had no enamel on them, and her baby teeth lost all theirs too. I also, suddenly lost my tooth enamel. We followed the advice in his book and it is working! No dentists, no expensive products. Just nutrition mostly.