Teeth are actually hollow. Not may people know that! If you look at a tooth in cross section, there is a hard outer shell called enamel, then the bulk of the tooth underneath the enamel is called the dentine and in the middle of the tooth is the nerve - the bit that hurts when you get toothache. The nerve enters the tooth through the tips of the roots, passes through a tube in the dentine - dentists call this a root canal - then passes into the middle of the tooth - called the pulp chamber. This nerve also has blood vessels.
Decay in the tooth means that there is bacteria living in it. These bacteria irritate the nerve of the tooth - and this causes the feeling of toothache. In fact, the bacteria can irritate the nerve so much that it dies - if this happens, it will then get infected - causing an abscess. At this point, if you want to save the tooth, you need the nerve cleaned out and the root canal of the tooth filled up. This is called root canal treatment.
Root canal treatment always seems to instil fear in people, but it shouldn't be so bad! Your dentist will probably take an x-ray of the tooth to check the shape of the root canals and to see whether there is any added infection around the root.
Firstly your dentist will remove the decay from the tooth and gain access to the pulp chamber. They will then remove the infected/inflamed nerve. The pulp chamber and root canals are then washed out with an antiseptic.
If the infection has spread beyond the tooth, he may have to give you a temporary filling and some antibiotics until it clears up.
The complicated part of the root canal treatment then starts. Your dentist has to find all the root canals - they can be tiny - and widen them out. They use very fine files to clean and shape the root canals ready for the root filling material to be put in. This filing process removes bacteria from the root canals. The final stage involves filling up these root canals with a rubbery like material called gutta percha. It is possible to do all of the above in one visit.
Sometimes the root canals are so fine and twisty that your dentist might decide to send you to a specialist called an endodontist to carry out the root canal treatment.
The success rate of root canal treatment is not 100% - various factors affect this - so discuss this and alternatives such as extraction before you start.