Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Beware of gum damage using this model!

I was a loyal user for years of the original Sonicare before it was sold to Phillips who designed this model. It worked wonders as I had no cavities for 5 years and no gum problem. Since "upgrading" to the 7500 I have gotten 1 cavity (on a receding gum area) and a detached gum using the "new model 7500. I attribute this to a smaller brush head which is a poor design that "overvibrates" on a smaller area loosening up the gums causing them to recede. The original Sonlcare cleaned over a wider area with a flat brush to evenly spread out the vibrations. I wonder if the original inventor had a hand in this "improved" model? If it ain't broken don't fix it! If you are a dentist or gum specialist,please take notice!!