Yes TBH I will probably be of limited help as without seeing your kid I can't really give particularly specific advice. But PM me and I'll do what I can.
Reminded me of one of those Telesales ads I saw in the States last year, like on QVC. They were showing a "new device" for cleaning things like the grouting in between tiles etc....saying "no more brushing and scrubbing"....it was basically an electric toothbrush (which seems fair enough as maybe previously you might have used a toothbrush or nail brush for doing it)....but it was at least twice the price of an electric toothbrush!
In answer to Supertyke and ES Saw these late. Leccy toothbrushes - yes. Most people remove plaque far more efficiently with an electric toothbrush. Doesn't need to cost the earth. The Braun 5000XL is a fine machine with change from £20. The Brauns last well with pretty low running costs in terms of replacement heads. Sensodyne toothpaste - also yes, but... it only works against a specific form of sensitivity. When the gum recedes slightly, the root of the tooth is exposed which has no enamel on it. The roof face is porous and the pores go right down to the nerve. Hence it is very sensitive. The active agent in Sensodyne causes calcium salts from your saliva to crystalise in these pores and thus block the path to the nerve. The problem is that generalised sensitivity due to large-scale root face exposure may be due to advancing gum disease, which Sensodyne will only mask symptoms of, rather than prevent and sensitivity localised to one small area may be due to tooth decay, especially if sensitive to sweet. So yes it does work and in the absence of any more severe dental problems, will improve matters. It is certainly worth getting your mouth checked out properly as well though (and no I don't mean by me in the dark at 11pm in Joseph Brammah's!!)