What can an emergency room in a hospital do for dental emergencies?

If it’s an infection they can give IV antibiotics. More often than you might think dentists undermeducated serious dental infections and sometimes the patient winds up in the ER.

Pain meds.

it depends. If it’s an abscess that’s causing pain then see above. If you’ve been in an RTA and knocked out all your teeth they’ll probably get you an actual dentist to sort it out (speaking from experience in the UK. YMMV).

If you fall or are in a car accident, they will sometimes pull out of your lip or other areas then send you to the oral surgeon/ dentist.