The default choice, and a good one

Boka did more than any other brand to move nano-hydroxyapatite from a Japanese pharmacy staple into American bathrooms, and the product has aged well. The formula is clean, the flavors are genuinely pleasant, and it is available at a price per ounce that undercuts most of the field.

It falls short of the top spot for two specific reasons. It uses nano-hydroxyapatite alone rather than a blend of particle sizes, and it does not publish the concentration. Neither is disqualifying. Both cost points in categories where the leaders are more forthcoming.

On the flavors

Ela mint is the one to start with. It is a soft, slightly herbal mint that most people find unobjectionable. The fruit-forward options are more divisive and worth buying one tube of before committing.