The dental pulp is a tissue that can suffer, up to the point of loosing vitality. The most frequent cause is the caries which, during its progression inside the tooth, may reach the pulp and damage it causing necrosis. But the caries is not the only factor causing pulpal trouble: there are other various possibilities. The tooth could find itself in an unfavourable biting situation, and suffer from traumatic contacts with other teeth, sometimes in a way so intense to cause an inflammation of modest entity that can degenerate in a non reversible pathology. Also the uncovering of the dental neck (the part next to the gum) may result in a thermic hypersensibility which, in its most severe form, leads to irreversible pulpitis.
Whatever the cause, when a dental pulp enters an inflammation phase, the same as in any other part of the body happens: a greater quantity of blood rushes into the tissue. The peculiarity of the dental pulp, however is that this increased blood quantity does not cause the tissue to swell, because this is impossible. The pulp, as a matter of facts is situated inside a rigid structure (the dental walls) and has thus no possibility to expand, so that it swells towards its inner side and compresses the nerve in a very heavy way. As a result the inflammations of the pulp (=pulpitis) are extremely painful: the classic tooth aching is one of the worst pains that can be experienced!
The compression of the nerve inside the tooth causes a status of pain and signals an inner issue. Within certain limits, this pathology can show up in a low intensity and show itself as a high sensitivity to thermic stimuli. In a sense, the pulp is able to compensate irritation effects, but of course only within certain limits. Once trespassed a given boundary, the pulp is no more able to compensate and gets ill in an irreversible way.
The pulp begins to be continuosly aching, it generates intense twinges and a pulsating pain which is unbearable. At this point, the pulp has no more recovering possibilities and must be removed: the tooth has to be devitalized.
c) Pulpal necrosis
The next phase in the pathology is the cellular death of the pulp and ceasing of its vital functions. At this point the tooth becomes a sort of bacterial tank, being colonized in its inner part by microorganisms producing dangerous toxines, progressing to the roots' exit, through the apex.
d) Abscess, fistula, granuloma, cyst
The flux of bacteria out of the dental apex causes a reabsorption of an osseous area around the apex, or a cavity in the bone itself. Basing on the infection's virulence, the bone can be reabsorbed up to its surface, perforating to the outside and having the gingiva swell in a classic abscess. This acute form is accompanied by pain and, occasionaly, by fever, but can also be limited to the swelling only. in some cases the perforation stabilizes and becomes an open canal linking the abscess to the mouth environment. this structure is a fistula. The tooth can stay in stand by this way even for years, without the osseous cavity getting larger, and even with the patient having no conscience of its existence. The fistula indeed, often appears like a small bubble giving no symptoms and draining to the outside the contept of the osseous cavity mixing it with saliva and food.
The abscess however is all in all a rather rare event: more frequent is the formation of a stable osseous cavity of chronic nature: the granuloma.
Even if from time to time the granuloma may provoke acute abscess episodes, it generally stays still. Sometimes the patient becomes conscious of its presence because the tooth giving it birth, becomes sensitive to chewing and to pressure.
The pain is typical because it can be easily located.
In specific phisical conditions, granulomas of older age may evolve into cysts. The cyst distinguishes itself from the granuloma because it has a periferic epithelium encircling the cavity and because it has a very defined radiological appearance. It can be assessed that a cyst does not hold bacteria, however this is a relatively unimportant feature. The most important fact is that a cyst very often does not receed with the mere removal of the bacterial charge from the tooth (root canal treatment) and has to be treated surgically.