I've got a few questions: 1) why is it better to use mouthwash with alcohol in it.2) won't that make you dehydrated?

A few answers. 1) the alcohol in the mouthwash helps control the bacteria around and between your teeth. Not sure if it is "better". All additional products will help along with proper brushing and flossing. 2) you do not drink the mouthwash. Unlike drinking alcoholic drinks that result in increased urination and possible dehydration after processing, the mouthwash is not absorbed into your body.