After using for two hours, zero removal of calculus [SEP] After using for two hours, zero removal of calculus. I will try again tomorrow. So far, only a headache from the vibration. The manual remover probably works better, at least I can see something removed when I tried it. I see absolutely no results with this vibrating unit. If I find a magical way to make it effective I will update this review.  Would definitely not recommend at this point.