My wife is fully aware of my abnormally high interest in orthodontics. In fact, it's the whole reason she got braces. Since her braces are fixed metal, they're obviously present in everything we do: travel, sporting events, concerts, the symphony, dining in and out, pubs, wine tastings, festivals, sex, etc.
One other person, my wife's best friend, is aware of the true reason she got braces. Other than that, we keep it very private in real life.