Right now
Keep any fragment
Put the piece in milk or in a clean container and bring it. Whether it can be bonded back depends on the break, but a fragment in a pocket is a real option and a fragment in a bin is not.
Cover a sharp edge
If the broken edge is cutting your tongue or the inside of your cheek, press a piece of sugar-free chewing gum or dental wax over it until you are seen. Twelve hours of a sharp edge does surprising damage to soft tissue.
Do not chew on that side
A cracked tooth splits further every time you load it. Eat on the other side, and avoid anything hard or crunchy entirely.
Rinse gently with warm salt water
Enough to clear debris. Do not poke at the break with a tongue, a fingernail or a toothpick.
Call
Describe what broke and how. You will be told whether it needs tonight or can wait, and if you are flying, say so on the call.
Why it gets worse quickly
Enamel is the hard outer shell. Under it sits dentine, which is porous and connects to the nerve through thousands of microscopic tubes. Once a break reaches dentine, cold air and cold water reach the nerve directly, which is the sharp shock you feel when you breathe in.
Left alone, that exposed surface takes on bacteria and the nerve becomes inflamed, and an inflamed nerve is a very different repair from a chipped surface. A break sealed in the first day or two is usually a single appointment. The same break in a fortnight can be a root canal.
How it is repaired
A small chip
Smoothed and polished, sometimes with composite added to restore the shape. One short visit and it is done.
A larger break, nerve not exposed
The surface is sealed and the tooth rebuilt in tooth-coloured composite the same visit, matched to the shade of the teeth beside it.
A break that reaches the nerve
The nerve is treated first, usually the beginning of a root canal, and the tooth is then rebuilt over it. This is still the same night. More on emergency root canals.
A crack below the gum
The X-ray shows how far down it goes. Some are restorable, some are not, and you will be told plainly which of the two you are looking at rather than sold a repair that will fail.
If you are flying
This is a common call. Cabin pressure changes are genuinely uncomfortable through an exposed dentine surface, and a sharp edge that is merely annoying at home becomes a fourteen hour problem at altitude. Say on the phone how long you have.
A break can usually be sealed and made airworthy in a single short appointment, with the definitive work done later or at home. Several of the clinic's Google reviews are from people who were treated a few hours before a flight.
Prices are published up front: the whole emergency visit is AED 1,500 to 2,500 all in, quoted after the X-ray and before anything is started.