Sonicare HX7990/02 UV Electric Toothbrush Sanitizer Review

I'm not sure if I just got a defective model or this product is just bad.  I read all of the directions and followed them very clearly.  It stated that it took 10 minutes for a complete cycle and then it shut off automatically.  I put it in at night before I went to bed.  When I took my toothbrush out the next morning, the head of it was different shaped as it had melted and where the brushes attach to the head of the brush had black on it.  I don't know if it didn't shut off and ran all night or what.  I haven't tried it again as I don't want to waste another toothbrush.  It's not like replacement brushes are cheap and I don't want to have to buy more.  Right now, I really can't recommend this product.  I'm not even sure if it really works - how would we know for sure.