Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good product

I have used this product about 5 times for 30 minutes each application. I have to say I am very satisfied. I noticed a difference the very first time and an improvement with each use. Of course this is not going to be as good as what your dentist can do, but it does a good job. My four year old son likes it too because I can't talk (or yell) with that light in my mouth!