Your body is capable of continual recalcification of teeth. Why doesn't it happen?
Two reasons:
1) most toothpastes contain glycerine that coats teeth and prevents calcification that is naturally applied to the outside of a tooth.
2) it requires a diet or supplementation that produces enamel.
If you have further interest, here is a link to a product sold on Amazon as a supplement. You must also switch to brushing with either non-glycerine soap as a substitute for toothpaste, or try very, very hard to find a toothpaste without glycerine.
Good enamel to you!
Monosodium Phosphate for building enamel at Swanson's Vitamins
After this, your homework is to determine why root canals are bad for you...
In a pinch, I have brushed with baking soda.
Do you have an opinion on using baking soda and a supplement?
During experimental periods of my life, I have brushed with Baking soda and peroxide, or with myrrh and some other herb, I think it was goldenseal. Would those combinations avoid the glycerine problem? Also is the link you provided the only answer to 2), or can you recommend other diet or supplementation to produce enamel?