I've had cleaning done about 1 month ago.  the d.h. did a great job of
removing
plaque and tartar buildup behind my lower teeth.  However, it's come
back.
I've done the recommended routine of brushing and flossing and
listerine.

I'm frustrated that plaque has built up behind that area.  It's not
easily accessible by my brush, so that's why plaque is building up in
that area.  I bought a pack of special dental picks called "brush
picks", but it's so damn hard to scrape the plaque off, especialy since
those picks are made of plastic.

I saw those Waterpik oral cleansers.  They have a water reservoir, and
attachments.

Are those any good?  Any advice on the removal of plaque buildup in the
affected area please?