Do I need to use toothpaste?
You can use the Ionic toothbrush with or without toothpaste since the cleaning action occurs through ionic action - reversing polarity to make teeth repel plaque - and not merely through the mechanical scrubbing action as occurs with other toothbrushes. (You have to use an abrasive like toothpaste with other toothbrushes to help with the mechanical cleaning, as with scrubbing a floor.)
The Ionic toothbrush on the other hand, makes teeth repel plaque and also attracts plaque to the toothbrush head, both due to Ionic technology. This means you do not have to brush so hard, which is better for the gums. You do need some fluid for the ionic effect to work - this can be water (a wet toothbrush head) or toothpaste, as per your preference.