What causes severe pain in tooth after a filling?

Several factors. : Deep cavities require deep fillings. Tooth colored fillings can contract and be sensitive for a while. Nerves from cavities can be irritated during the filling process, so the nerve can become inflamed enough to then need a root canal. If the filling is to "high" or the bite is to hard, then the tooth can become sore and sensitive also.

Couple of reasons: 1. A high bite after the filling. 2. A void inside the filling. 3. The filling is too large or deep which is close to the the nerve and the tooth is not responding well becoming symptomatic to hot and cold which may lead to a root canal. This is a natural risk in the procedure. 4. There could be exposed dentinal tubules which are sensitive to hot and cold, sweets or acids like lemon or lime.

See Dentist ASAP: Please see the dentist who filled the tooth asap... One possibility is that the filling is high. A slight adjustment may resolve it completely. Or... The filling may be very close to the nerve. This can lead to a root canal or loss of your tooth. Aleve, (naproxen) advil, Motrin or for more holistic patients, arnica can be helpful to reduce swelling and pain temporarily.