Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Seek emergency help for trouble breathing or swallowing, rapidly spreading facial or neck swelling, or a severe allergic reaction with widespread hives, faintness or breathing difficulty.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Contact the dental clinic promptly if:
A temporary or permanent crown becomes loose or falls off
Pain is severe, worsening or keeps you awake
You develop increasing gum or facial swelling
The crown breaks or the underlying tooth is exposed
You have fever along with dental pain or swelling
3
Does any of this apply?
Book an appointment
Arrange a routine dental appointment if sensitivity continues, your bite feels uneven, the crown edge irritates your gum, or food collects around it.
The article also says
If a crown comes off, keep it safe and do not use household glue to replace it.
Every sign above is quoted from the sofidex article on Dental crowns. If you are not sure, err upward — it is always reasonable to be checked.