Can inflamed periodontal ligament be confused w infection and/or periapical absess? look similar on xray?also told vital tooth,coldtest=no infection?

Great Question: You are correct, a vital tooth should have no abscess (no infection). But I've encountered situations on multi-rooted molars where one canal is vital and the other may be non-vital due to trauma (no infection). It is rare, but I've seen it. That's what makes answering your question, sight unseen, difficult. If your dentist is having difficulty, see a local endodontist.

See your dentist: The differential diagnosis of endodontic and periodontal diseases can sometimes be difficult. However, the dentists are well trained for proper differential diagnosis and selection of treatment.