X-ray shows infection above upper molar tooth which is causing swelling of left side of face. Tooth does not hurt,since it already has had a root canal. Is this something a dentist can take care of or do I go to a regular doctor.

I would see a dentist.

I would see a dentist.

Not necessarily. OP needs an endodontist to diagnose the proper procedure. Root canals, if not done properly, develop fissures, or cracks in the molar submerged in bone. Infection will have to be drained, if any, but suspect this is the case.

Of course, diagnosis cannot be given on the Internet. This is just a general opinion.

I think if you call a dentist and recite your symptoms , they can tell you if this is something they can handle or refer you to an oral surgeon.

How did you manage to get an x-ray in the first place without a dentist ? If a dentist did the x-ray , you should already know the answer to your question.

I have never been able to 'call a dentist and recite symptoms' hoping to get a determination. That is just not possible even if you do manage to get past the receptionist. No dentist worth it will give this information over the phone. They don't make any money that way.

Why would a dentist diagnose over the phone without even seeing what the client is describing?

You probably have a 'Periapical Abscess' above the tooth that has been treated. This occurs at the end of the tooth's root and cause inflammation. Bacterial Involvement is Obvious.
An Endodontist is A Dentist itself... I would suggest you to visit an endodontist or an oral surgeon. Nothing grave ! They will drain the abscess and put you on some anti biotics
Please remember this 'diagnosis'is based on what I just read.. if I have a look at you and the x ray I could probably tell more.
There are chances of your maxillary sinus being affected too.
Consult a the above Dentists ASAP.
Cheers

A Dentist. A dentist can prescribe antibotics, and would, normally, be better than an MD doctor at determining what type of antibotics. Good luck.