On a panoramic radiograph, what type of root resorption is most likely occurring when an impacted third molar shows resorption confined to the external root surface (originating from the periodontal ligament side), rather than from within the canal?

External resorption originates from the periodontal ligament/external root surface (often from pressure of an adjacent impacted tooth, cyst, or tumor, or from orthodontic forces), in contrast to internal resorption, which originates within the pulp canal space following pulpal inflammation. Radiographically, external resorption typically appears more irregular and may be superimposed over (rather than centered symmetrically within) the root canal outline.