What other symptoms might he be having? The reason I ask is because I have a child with celiac disease(or coeliac if you live in the UK) an autoimmune disease where the body can not tolerate gluten, a natural protein found in wheat, rye, oats or barley(malt). In small children, this often shows up in bad teeth, weak enamel, breaking teeth, yellow teeth, just overall bad teeth. My mil has this disease and her dentist told her that if he didn't know her & how well she takes care of her teeth, he'd swear she never lifted a toothbrush to her mouth her teeth were so bad.
It is an inherited disease, not one you can catch by contact, and while there is no cure or medication, there is treatment, a gluten-free diet. Not as impossible as it sounds.
I just thought I would put that out there for you to consider. You can read more about this disease at http://csaceliacs.org/