Root Canal before Crown?

I have an upper right molar (with a crown) that has an absess and is in need of a root canal and a crown replacement. I have been taking an Antibiotic since Friday (the gum is still tender where the absess is)The dentist is insisting that I come in Monday to start on the crown before I have the root canal down. She wants me to have a temporary crown on BEFORE going to have the root canal done. This is a new dentist (yes, one that is on the insurance) and I am already having questions on some of the decisions I have allowed her to make for me. She has prescribed Captek crowns for 3 of my molars with the explanation that a Captek crown would be better for me because of periodontal disease. Are the Captek crowns really so much better than say a crown with semi-precious metal for warding off plaque? I have not been able to find any kind of comparison for such anywhere and I am feeling that a semi-precious PFM would work just as well as the Captek (more expensive) model. So, I guess there are 2 questions here...Root Canal before Crown work? and Captek or semi-precious PFM?
Thanks for any help you may give! Tweet