I have been using the Sonicare 9900 prestige ultrasonic toothbrush for a week now. Its sensors report to the Sonicare App on my iPhone. While you are using the toothbrush the App is coaching you on how you are doing it. moving to much, too much pressure. it divides you teeth up into sections that you address one at a time. The toothbrush senses were you are in your mouth outside, and inside of your teeth. At the end is grades how you did and how you can improve it. The thing I learned was I was pressing to hard the Sonicare toothbrush is ultrasonic and does not need much pressure and movement to do the job. Watching my progress on my iPhone is a real treat. Yet another reason my iPhone has become an indispensable part of my life. The 9900 is not cheap for a electric toothbrush but visiting the dentist isn't cheap either.