I went in to the Zapper Forum to see if anyone would talk about it.
No bites there.
I don't like the idea of putting a magnet to my teeth and gums area,
because it stirs up a hornets next, espcially if one has silver and/or
gold, it can reverse the polarity and cause more pain. I don't think
any of the lower frequencies help tooth/gum pain either, at least not
mine and I've tested up to 1600Hz. I had much better luck shooting for
the Clark frequencys, most in the 350KHz range.
No reason one couldn't add a little charge to a water pik though.