How do you tell an adult they need dental work?

A friend recently started seeing someone. In so many ways she is perfect. Very stable well paying job. Cool about children from a previous marriage. Attentive and already meeting the family. Only issue: She is actually missing a few teeth. In all other ways they are very fastidious about their appearance. It is hard for my friend to consider intimate or long term relations due to this issue. Is there a polite way to mention it or inquire?