Review (5/5): Surprise!  It works.  But beware the dispenser!
I bought this at the same time as Colgate Sensitive Pro-relief Enamel Repair Toothpaste, 2.5 Oz (Pack of 2) https://www.amazon.com/dp/B013R1RON4/ref=cm_sw_r_taa_oZX0xbR62JNZK
May you never need such intense treatment, but I chipped a tooth, leaving rough edges. So it was fix or replace it. I have been using the gel at night in a mouth guard and in less than two days, the damaged edge is smoother. I can't keep this up forever, but I am sold on the idea that you can replace calcium.
I still use my favorite toothpaste and rub the Colgate into all the thin ends of my teeth. The result is worth the effort.
Update: At first, I thought I was doing something wrong but dried gel at the end of the tube consistently squirts out more than I want, but I can spread the blob over the bottom and top teeth guards and it definitely works. Small inconvenience for relief.