External Resorptive lesions are often fairly easy to diagnose radiographically. As I have written in other parts of this website, external resorption has its origins in the attachment apparatus and is not related to the pulp per se. We usually look for radiographic evidence at or near the bone crest. The pulp may become involved if the resorption is severe, but often there still is a thin layer of dentin over the pulp, which gives these lesions their ghostly characteristic appearance. Therefore endodontic treatment of the tooth is often a sequela to attempted resorption repair (often due to extreme thermal sensitivity caused by proximity of the restoring material). The Endodontic treatment is incidental and NOT therapeutic for the lesion by itself.
Some of these smaller lesions are treated by first flapping the area, determining the extent of the resorption (whether it is restorable) and then restoring the resorbed area with a material such as Gerestore. Restoration is most often performed in anterior teeth or in aesthetic zones as an alternative to extraction of a tooth, which in many cases is otherwise virgin. As Heithersay has written in his extensive articles on resorption, the only factor that many of these patients have in common is a history of Orthodontic treatment. This is not the case in this patient.
A right maxillary second molar #17 was referred to me for endodontic consideration because of an external resorptive lesion (Fig.1). There was no history of Orthodontic treatment (one of the few correlating factors that are associated with external resorption in teeth.) The referral was fairly sure that the tooth was not restorable but wished a second opinion. He was considering extraction of #17. His referral film showed extensive distal resorption and non restorable tooth. This was confirmed in the mouth.
In order to perform a proper radiographic examination, my office always takes a bite wing image (Fig.2) of all teeth, so we can assess the bone levels and relative proximity of all restorations to the pulp. We were very surprised to see undiscovered asymptomatic external resorption in the opposing mandibular second molar #47. This resorption was almost as large as in that #17. This was important to note, because #46 had previously been extracted. If the referral was contemplating restoring the occlusion on this side with a mandibular 3 unit bridge, this would now be impossible. It appears that both teeth (#17 and 47) would now be lost and that the treatment plan would have to be radically changed to include replacement of the #46 with an implant. In that way, although we lost both second molars, reasonable posterior function could be recreated for the patient by giving #16 an opposing implant. One final consideration is that the supraerupted #16 might also require a crown to bring it back to a proper occlusal level and make room for the implant crown.
It is important that you examine all facets of the prospective treatment in a case, regardless of how obvious the diagnosis may seem. Had we not taken a BW film (in what was seemed to be an unsalvageable #17), we would likely have never seen the resorption in #47 because it would be difficult to see clinically in the mouth. (It was at the level of the distal CEJ). It is possible that we may have told the patient that although we were extracting #17, the opposing arch could be reconstructed with a bridge #47-45 and we would have been in error. There are also financial consequences for the patient because while most insurance plans pay for fixed bridgework, few if any, pay for implants. What appeared to be a simple “I don’t think #17 is restorable, could you have a look?” now becomes a much more complicated treatment plan that involves both arches on this side of the mouth and an implant.
Fig. 1 Preop #17 Referral Film
Fig. 2 Bite Wing
Fig. 3 #46 extracted, #47 External resorption