There are several reasons why teeth may hurt and each call for different interventions.
A tooth may hurt if it is broken, loose or if it has a cavity (a hole in the tooth where bacteria have entered resulting into tooth decay). Cavities are the usual cause of tooth aches. The dentist is able to examine the affected tooth and decide on how to treat it.

The removal of a decayed tooth is performed if the tooth is too far destroyed from the decay process to effectively restore the tooth.
Extractions may also be preferred by patients unable or unwilling to undergo the expense or difficulties in restoring the tooth. 
The dentist may decide to take out a tooth if:
. It is grossly injured  and will probably cause further problems in the future
. The cavity is deep and has formed an abscess. An abscess occurs when germs from tooth decay start an infection on the inside of the tooth and form pus.
A Person with such tooth decay will have these signs:
. A swollen cheek and gum near the bad tooth.
. The tooth hurts constantly, even when the person tries to sleep.
. The tooth hurts sharply when you tap it.
Such a tooth should not be filled because the filling material will cover up the germs causing more pain and swelling. However, the dentist may perform a Root Canal Therapy (RCT) to save the tooth. 
The tooth cavity can be filled if:
. There is no swelling of the cheek or gum near the tooth
. The tooth hurts only once in a while.
. The tooth feels the same as the others when you tap against it.
Early filling of tooth cavity helps to stop the decay from growing deeper, and developing a tooth abscess.
A filling may be permanent or temporary. A permanent filling is made to last for many years while a cement filling is a temporary filling, meant to last only for a few months until it is possible to get a permanent filling.
Consult a dentist as soon as possible to save your teeth.

Christine Namatovu is a Clinical Officer at Allan Galpin Clinic, UCU