Actually, it’s even worse than you suspect. That is, dentists, orthodontists, periodontists, and oral surgeons, while they work closely with each other all the time, are really unto themselves. As a glaring example, dentists and orthodontists don’t even use the same numbering system for teeth.
They do, however, have strict limits on what each of their specialties does, and the order in which they do it, based on what the problem is.
As far as relating to other doctors, however, it is more problematic. I suspect this is because referrals are to a great extent limited from them to internists, not the other way around. In this way, dentists often act as GPs for all sorts of oral problems, and problems reflected in the mouth that only their diagnosis and experience would detect.
Unless a problem is glaringly obvious, a GP would send someone with any oral problem to an ear, nose, and throat specialist, or a gastroenterologist. But for example, in the case of my Aunt, they would look everywhere but the mouth for problems. They would even suspect a brain infection first. And it certainly didn’t help that she was elderly, with reduced mental capacity at the time.
I think they finally diagnosed her problem after months because she had a routine dental check-up.
In any event, there are reasons why the two branches of medicine have drifted apart. It might not be the best situation, but it is not done for petty reasons.
As an aside, I had a cousin who was a dentist, and while driving halfway across my State, I got a two-hour rant about the FDA. Seems that they had decided to ban some black, tarry goop that dentists had been putting in tooth sockets for over a hundred years to stave off infections, because if you ate several ounces of it, you would get sick. But there was no alternative available at the time.
So the FDA was willing to accept perhaps 30,000 serious dental infections annually, in exchange for banning the stuff, which in a hundred years had not sickened a single person. Needless to say, my cousin disagreed. A lot.
My best friend was fighting multiple serious infections and they couldn’t figure out why.
The doctor checked her heart and heard a murmur, and commented that next time she had dental work, she’d need to go on anti-biotics beforehand as a precaution. My friend then told the doctor that her symptoms actually started after her last cleaning, which she had not made the connection before. She said the doctor actually blanched because she finally figured out what the problem was; my friend was going septic.
She was on three very powerful anti-biotics for several weeks to finally clear up the infection. At the rate she was going, if they hadn’t caught it, she likely would have died from it.