External root resorption is may be 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.