waterpik, root canal, whitening

Hi, I have several questions - have been using the travel version of waterpik for a while and really like it. Is it a replacement for flossing or should I floss as well? I also am waiting for treatment of an abscess on a root canal, I'm confused as to whether to get the root canal refilled, or wait for an apicectomy under general anaesthetic. I was told that after apicectomy the gum will recede, and 50% chance of tooth loss. Also, are there any natural tooth whitening products?