My teeth got really sensitive on my 24 day Master-Cleanse I ended 10 days ago. I went to the dentist and he told me it was good to rinse the mouth with water after you drink the lemonade every time. Also, he told me NOT to brush my teeth for a while after drinking the juice since the enamel is week then.
Try to drink the lemonade as few times as possible throughout the day or you'll constantly be supplying fresh Sugar for the bacteria in the mouth to feed on.