I have periodontitis and I need treatment, but I also need some new fillings, crowns and root canal treatments. What should I have taken care of first?

The treatment of periodontitis should definitely be completed before any new prosthodontic work (meaning a new crown or bridge). If the crown is placed first without treating the inflammation which is caused by periodontitis, the inflammation will then worsen. Another reason for the periodontal treatment to go first is that the gum line will probably be at a different level after the periodontal treatment. So if you had a new crown done and then you had done your periodontal treatment, it is very possible that the margin of the crown will show due to a change in the gum line.

If you need new fillings done, these should also be taken care of after the finish of periodontal treatment, unless a tooth is in pain. In this case there might be need for root canal treatment which will go first.