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Inside Dentistry
April 2018
Volume 14, Issue 4

For Internal and External Resorption Cases, What Criteria Govern Your Decision to Treat or Extract a Tooth?

Allen Ali Nasseh, DDS, MMSc | Martin Trope, DMD | Alex Fleury, DDS, MS, FACD

Allen Ali Nasseh, DDS, MMSc: The incidence of internal and external root resorption appears to be on the rise. Whether this is due to a higher incidence of elective orthodontics, trauma, or idiopathic reasons remains unknown. Both internal and external root resorptions can be benign and slow growing or aggressive and fast growing, resulting in tooth perforation, attachment loss, and consequent tooth loss secondary to endodontic and/or periodontic infections. The question of whether a tooth with resorption is salvageable through conventional root canal therapy and surgical root repair or if it should be removed is dependent on a few factors: the stage of the disease process, the location of the lesion, and the availability of surgical access to the site for adequate curettage and repair of the defect.

For internal resorption defects, early diagnosis is key and leads to a better prognosis. Extensive internal root resorption with root perforation can leave a tooth biomechanically and periodontally compromised. Furthermore, necrotic teeth tend to do slightly worse than vital teeth in both internal and external resorptive defect cases. Nevertheless, internal resorptive cases have a good overall prognosis as long as the tooth is periodontally sound. For external root resorptions, triage is equally important. When resorption is subgingival and surgically accessible, the prognosis is much better than when it's associated with invasive cervical root resorption involving the attachment apparatus and is surgically inaccessible. Heithersay has classified root resorptive defects into categories in which Class 1 and Class 2 lesions have the best prognoses and Class 3 and Class 4 lesions have worsening prognoses, respectively.

Ultimately, surgical access to these lesions should be considered as the main clinical factor in the decision to initiate endodontic therapy. Assessment of the extent of the lesion and the evolution of surgical access for repair following root canal therapy is only possible through quality periapical radiographs and cone-beam computed tomography (CBCT) imaging. Today, highly biocompatible root repair materials are available for subgingival root repair. The key, however, remains the availability of surgical access for effective repair. Thorough clinical and radiographic testing can paint a more accurate prognostic picture for conventional treatment while anticipating the need for surgical repair following this treatment. Therefore, an understanding of prognostic factors and great patient communication are the most important criteria when deciding to save or remove a tooth with extensive internal or external root resorption.

Martin Trope, DMD: The survivability of the tooth after treatment is the overriding factor to consider. For internal root resorption, the potential for survivability after treatment is usually very good. Because the defect is internal and the nutrients to the resorbing cells come through the root apex, the first challenge involves using root canal treatment to stop the advancement of the defect by cutting off the blood supply to the resorbing cells. The next challenge is to remove the soft tissue and fill the defect with a reinforcing restorative material. Both of these challenges can be easily met with new technologies and materials. Therefore, unless the defect is huge and the remaining walls extremely thin, the prognosis for survival is excellent.

External root resorption is much more difficult to treat. For these defects, the blood supply to the resorbing cells is in the external periodontium. As with internal root resorption, the blood supply to the resorbing cells must be cut off first, and then a biologically acceptable restorative material placed afterwards. When the resorptive defect is coronal, it can be approached like caries by removing the soft tissue from the tooth and bone and then restoring the resultant space with a well-sealing, non-toxic restorative material. However, achieving these goals is extremely difficult when the resorptive defect is apical to the bone level, which unfortunately happens more often that not. Oftentimes, in order to cut off the blood supply to the resorbing cells and create a margin for a biologically acceptable restoration in these cases, the existing attachment must be sacrificed to such and extent that the survivability of the tooth, as well as the adjacent tooth, comes into question.

Some have tried an internal approach to treat external root resorption by using strong acids to burn the resorptive cells and then sealing the tooth from the inside with the hope of creating a barrier to halt further resorption. To accomplish this, a root canal treatment needs to be performed in order to gain internal access to the resorptive defect, and it is important to note that a "blind" approach with strong acids has its own risks. With this approach, the more apical the defect, the less likely a positive outcome will result.

Alex Fleury, DDS, MS, FACD: The aim of endodontics is the prevention or treatment of apical periodontitis with tooth preservation as the ultimate goal.

 It only seems fair to our patients that this attempt to save teeth ensures long-term success and not simply the addition of another year or so in function.

Not too long ago, few were the alternatives for a tooth with a compromised prognosis, such as those affected by resorption. Resorption can be an aggressive event at times, and the question of whether a tooth can still be saved or not arises.

Resorption may have many different etiologic factors, but it often occurs as a complication of traumatic injury to the teeth. Resorption can be transient, such as in cases of orthodontic movement, or progressive, such as in cases of internal resorption or external inflammatory resorption.

Resorptive processes significantly lessen the prognosis of a tooth's retention due to loss of tooth structure and periodontium and must be taken into consideration when deciding to save a tooth or to extract it and place an osseointegrated implant.

Clinically, the main factors that should be taken into consideration in this decision-making process include the following:

Medical history. Due to a complicated medical history, not all patients are good candidates for dental implants or other surgical interventions. A patient's systemic condition, the quality of their bone, and habits such as smoking can compromise the long-term success of dental implants.

Tooth restorability/degree of resorption. The decision to save a tooth or not is largely dependent on how much tooth structure remains. If the degree of resorption is such that the remaining healthy structure is insufficient to support a restoration in a predictable manner, the tooth should be extracted. It should be noted that the decision to save a tooth or not is greatly facilitated by the use of a CBCT study, which allows clinicians to see how much tooth structure is left in different planes.

Type of resorption. Different types of resorption have different prognoses that range from favorable to hopeless. For example, internal resorption has a favorable prognosis, and it is relatively simple to halt. A root canal treatment will stop this resorptive process because the clastic cells involved in internal resorption reside in the pulp tissue. Cervical resorption (ie, peripheral resorption), which is not an endodontic disease, will not be arrested by endodontic treatment. The prognosis for this type of resorption is poor. External inflammatory resorption can have a favorable prognosis if the secondary stimulation for the resorptive process is a root canal infection. In these cases, once a root canal treatment is performed to control the process of the infection, repair of the resorption lacunae will occur. In ankylosis and replacement resorption cases, the process cannot be stopped because it is basically a physiologic function of the body. After an area of the root is denuded from the periodontal ligament (eg, from trauma), clastic cells start to resorb the tooth structure and replace it with bone, as part of a natural process. These cases have a hopeless prognosis. The younger the patient, the faster the process of replacement resorption will totally destroy the tooth.

Allen Ali Nasseh, DDS, MMSc,

is the president and CEO of Real World Endo and maintains a private practice in Boston, Massachusetts.

Martin Trope, DMD,

is the creator of Next Level Endodontics and maintains a private practice in Philadelphia, Pennsylvania.

Alex Fleury, DDS, MS, FACD,

is an assistant professor at the Baylor College of Dentistry and operates a private practice in Dallas, Texas.

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