Actually works!
This came already charged.  No batteries, is a usb charging device.  I had bad black tartar on the backs of my front teeth, and this little tool got it all off.  I was skeptical about how well a home tool would work, but I am pleasantly surprised.  It was also gentle with my gums.  I would recommend this product as a great tool for in between dental visits, but not in place of them.
Rating: 5 stars