Hello and welcome to the Pain Management Forum. I am glad that you found us.
I am not an expert but I think your dentist's concern is unfounded. However the best information on medications and their interactions is available from your local pharmacist.
You dentist's concern may come from the fact that the use of an SSRI (citalopram is one) with aspirin, nonsteroidal anti-inflammatory drugs (NSAID) or other drugs that affect bleeding may increase the likelihood of upper gastrointestinal bleeding. A pain medication such as vicodin which is usually prescribed by dentists, contains acetaminophen which is not a NSAID and does not effect ones bleeding rate. Your dentist may need a course in pharmaceuticals.
I've had several root canals and they have caused me pain in the 24-48 hours following the procedure. It is common practice in my area to prescribe a pain medications post procedure.
Maybe your pharmacist will have some literate you can take to your dentist.
Good luck with the root canal. I hope all goes well.
Tuck
I'd find a different dentist! Citalopram is an antidepressant (I was on it once), I took it along with my pain medications without any problems (MScontin&oxycodone) for a long, long time. I never had any pain medication for my root canals. I didn't need it. The novacaine works well during he visit. I don't think root canal should hurt in between visits for them either. This was long ago, maybe I'm remembering wrong, but I don't think so! Good luck.