How to prevent cavitations after extraction

I just had a root canaled tooth extracted(#1) today and am wondering what I should do tomorrow along with salt rinse to prevent cavitations.

Also another question: if there is no infection present in a root canaled tooth(#8) and on an x ray the bone seems to be healing after a year since the RT treatment, and growing back above the root canal, could it mean that the tooth may be good and there is no cavitation? are root canaled teeth without symptoms and seemingly good on xrays safe?