The most important constituents are fat soluble vitamin A + D and K2.
How I get these is a good cod liver oil supplement such as Rosita or Greens Pastures (A, D) and grass fed butter, Anchor or Kerrygold are good enough (K2). You should eat these at the same time, I notice my teeth looking whiter and they feel stronger like a new layer has been created within hours.
So. This will remineralise your teeth like no tomorrow. All other recommendations for me help but without these vitamins in this form you are fighting a losing battle, for me anyway.
For more information on this look up a guy called Ramiel Nagel who wrote a book called "Cure tooth decay", and researched a guy called Dr Weston Price who found out this information many decades ago.
Also you should avoid glycerin and fluoride in tooth paste.