After nearly 10 years of use, our original Sonicare toothbrush finally gave up the ghost. It was happily buzzing along one day, and completely dead the next, with no warning (and right after I purchased new replacement heads, naturally).

     I searched to replace the original Sonicare, as it worked well, and I had the new replacement heads that were expensive and barely used. The stores I checked no longer carried the original model, but stocked the ProResults Sonicare instead.

     It was expensive, with very little price difference between stores I checked. Based on the new...