Hmm if you dropped all the tables then the dummy content should be gone though. Anyways, luckily there’s also an easy way of doing this in WordPress. Simply go to the posts and pages page, and select all posts/pages like this: http://cl.ly/image/2A2B0o3I1E34. Then move them all to the trash. Do the same for the categories and menus. This way you can remove all content with just a few clicks 🙂
Hope this helps!