Summary
If a tooth has become infected or seriously decayed, a root canal can save it. Without treatment, an abscess may form.
During a root canal procedure, the pulp and nerve are taken out of the tooth before it is then cleaned and sealed.
The big picture
A tooth is basically made of four different parts. If we work inwards, then the outer layer that we see is the enamel. This is a very hard substance and is not sensitive in any way. It has no real cellular component and we can bite on it or brush it and it will not hurt. It is what makes our teeth look white.
The body of the tooth is made of dentine and, while it is hard, it has many small tubules that run outwards from the nerve and these contain little ‘tendrils’ from nerve cells that run from the nerve to near the surface of the tooth. These are what cause sensitivity to cold and tooth brushing in some people. If the dentine is exposed by a fracture or a hole, then the tooth gets sensitive.
The inside of the tooth is what people call the nerve or pulp of the tooth. This is actually a collection of nerves, blood vessels and connective tissue. It is very much like any area of tissue in the body except for one thing. It is constrained inside a solid tooth, and as such cannot swell up if it gets any minor injury. The blood supply into the tooth is through very tiny holes right at the base of the root, and relatively minor traumas to the tooth or nerve can lead to the tissues trying to swell up which simply increases the pressure inside the tooth. As a result, less blood gets in and so the tooth can get very sensitive, and then ache, and then the tooth dies. This can bring about a cessation of the pain, but we have an area of dead tissue with no blood flowing into it. All it takes is bacteria to move in and they have a ready supply of dead tissue in which to breed. These then start to get out the base of the tooth and infect the bone, and then the tooth becomes tender to touch or bite, and there is an abscess in the bone, with or without severe pain.
The outer layer under the gums is the cementum layer that helps in attaching the tooth to the periodontal ligament and then to the bone. The dead tissue has to be removed. There are only two ways to do this. The tooth has to be removed, or the nerve / bacteria have to be removed from within the tooth.
The procedure is normally in two basic parts. The first is the removal of the dead tissue, scraping the canals smooth, chemically disinfecting and sterilising the tooth and then sealing in an antibiotic mix of some form to ensure that the tooth is sterile and that the bone around the base of the tooth can heal. The second is the re-washing and sterilising of the tooth, and then the sealing of the tooth with a mix of special cement and an inert point. Sometimes this is simple, and then sometimes the nerve canals are twisted and blocked and incredibly thin. Not all teeth can be fixed by a root canal treatment, notably those with a fracture through the tooth root as well.
