Black mold is revolting [SEP] I got this brush because my dentist recommended it. I tend to brush too hard on the corner teeth and was creating notches. I was very happy with this -- for awhile. After using it for awhile I started to notice a nasty smell. I cleaned the outside of the brush and that didn't help. Next I unscrewed the base from the brush and it was pretty bad in there. There was black mold as well as thick white gunk. I cleaned it thoroughly with bleach, getting into corners with q-tips. In no time, the smell was back. This time I investigated further into the brush head itself. Gaaaaack. There was a lot of gross mold growing in there. I soaked that in clorox, then gave it a shake. Chunks of mold came flying out. I cleaned it as well as I could and reassembled it. The brush head no longer worked.<br /><br />I change the replacement heads pretty regularly, even though they are very expensive. I am going back to a regular brush with soft bristles that I can buy for a couple bucks and toss when it gets old.