External resorption

There are many causes of external resorption, both general and local. An alteration of the delicate balance between osteoblastic and osteoclastic action in the periodontal ligament will produce either a build-up of cementum on the root surface (hypercementosis) or its removal together with dentine, which is external resorption.

Resorption may be preceded by an increase in blood supply to an area adjacent to the root surface. The inflammatory process may be due to infection or tissue damage in the periodontal ligament, or, alternatively post-traumatic hyperplastic gingivitis and cases of epulis. It has been suggested that osteoclasts are derived from blood-borne monocytes. Inflammation increases the permeability of the associated capillary vessels, allowing the release of monocytes which then migrate towards the injured bone and/or root surface. Other causes of resorption include pressure, chemical, systemic diseases and endocrine disturbances.

Internal resorption

The aetiology of internal resorption is thought to be the result of a chronic pulpitis. Tronstad believes that there must be a presence of necrotic tissue in order for internal resorption to become progressive.

In most cases, the condition is pain-free and so tends to be diagnosed during routine radiographic examination. Chronic pulpitis may follow trauma, caries or iatrogenic procedures such as tooth preparation, or the cause may be unknown. Internal resorption occurs infrequently, but may appear in any tooth; the tooth may be restored or caries-free. The defect may be located anywhere within the root canal system. When it occurs within the pulp chamber, it has been referred to as  pink spot  because the enlarged pulp is visible through the crown. The typical radiographic appearance is of a smooth and rounded widening of the walls of the root canal. If untreated, the lesion is progressive and will eventually perforate the wall of the root, when the pulp will become non-vital (Fig. 7a). The destruction of dentine may be so severe that the tooth fractures.
The treatment for non-perforated internal resorption is to extirpate the pulp and prepare and obturate the root canal. An inter-appointment dressing of calcium hydroxide may be used and a warm gutta-percha filling technique helps to obturate the defect (Fig. 7b). The main problem is the removal of the entire pulpal contents from the area of resorption while keeping the access to a minimum. Hand instrumentation using copious amounts of sodium hypochlorite is recommended. The ultrasonic technique of root canal preparation may provide a cleaner canal as the acoustic streaming effect removes canal debris from areas inaccessible to the file. The prognosis for these teeth is good and the resorption should not recur.