Historically, classifying systems for resorption have been insufficient to adequately guide the treating doctor and inform decision making in the clinical management of resorption . Words like inflammatory and replacement as identifiers are less than ideal as all resorption is inflammatory and all resorption involves replacement. Identifiers using cervical when used to describe ECIR are not really accurate either and are really misleading as the resorption typically stems from the level of the crestal bone. For these reasons, based on more current models, I use a clinical model of classifying resorption, and subsequent management thereof:
The initial identifiers are based first on the derived process location- either external or internal. It’s important to note that the identifiers are derived from imaging, most often CBCT imaging.
Internal Resorption is derived from the pulp. The presentation can be with either a vital or necrotic pulp. Additionally, the resorption can be further classified by extent- namely non-perforating, or perforating. Internal Resorption that is perforating may require surgery to adequately manage the case. Often the process involves a vital pulp, however, occasionally, the pulp may be non-vital. From a prevalence perspective, internal resorption is low; it’s rare. With internal resorption, since the process is pulpally derived, the replaced tissue is radiolucent. There is not a bone deposition component to internal resorption.
Internal resorption with a necrotic pulp:
Internal Resorption with Perforation:
External resorption refers to the process of tooth structure being removed and replaced from the outside. Additional identifiers depict distinctions based on a mix of location, cause, and extent. External Crestal Resorption is by far the most common type of resorption. It originates at the level of the crestal bone. A mix of soft granulomatous tissue and hard boney tissue invade and replace the tooth. Additional identifiers include scooping or tunneling. Scooping refers to the pattern of extension by which it progresses in a relatively bowled out fashion as if the tooth removal was performed with a small ice cream scoop. Tunneling refers to a thin fingerlike progression, often many of them progressing axially. Finally, the extent of the External Crestal Resorption may be described. Mild refers to external resorption that doesn’t involve the pulpal space. Moderate is likely to involve the pulp space and will require endodontic therapy. Severe resorption is the extent whereby the tooth is usually no longer restorable. The determination of restorability is made via CBCT. One thing to keep in mind when determining the extent of the resorption is the hard tissue component invading the tooth. It’s easy to mistake tooth schema for invading bone or bone schema. Additionally, the pdl is not present in this area making the distinction more difficult. Sometimes, changing the scale of the imaging during viewing can help. That’s because the process of interpreting schemata is itself dependent on scale. For example, we understand that mouth is part of face, and lips are part of mouth, and vermilion border part of lips. Changing the scale helps with understanding features at all levels.
External Crestal Resorption, Moderate Scooping:
External Crestal Resorption, Severe, Tunneling:
Tunneling Resorption presents challenges as the osseous tissue embeds itself axially. Aggressive removal weakens the tooth, however, leaving bone behind allows for resorptive progression.
External Apical Resorption:
External Apical Resorption can be a result of orthodontic force, root canal infection, or in some cases, unknown causal relation.
External Pressure Resorption:
Teeth and expansile growths such as cysts can cause pressure resorption. Depending on the restorability the extent may be mild, moderate, or severe.
External Axial Resorption:
External Axial Resorption is identifiable by the radiolucent areas adjacent to root structures. Often this is sequela of trauma and accompanied by an infected tooth. This resorption may be arrested by endodontic therapy and medication with calcium hydroxide. The extent of the injury and development of the tooth determines the prognosis. Often injuries to these teeth include avulsion, lateral luxation, intrusion or extrusion. Depending on the extent of External Axial Resorption, External Ankylotic Resorption may follow over time.
External Ankylotic Resorption:
External Ankylotic Resorption may follow after External Axial Resorption. The difference is the lack of radiolucent areas adjacent to the root. As with other external resorption where bone deposition is involved, distinguishing between root and bone schemas can be difficult. The appropriate interpretive response is increased uncertainty. In the developing adolescent, when facial development is not complete, the management of External Ankylotic Resorption is decoronation. An alternative might include autotransplantation if there is a knowledgeable and skilled surgeon.