A tooth that received root canal treatment one week ago shows a radiopaque area at the apex and a radiolucent gap between the temporary filling and the gutta-percha. What does the radiolucency between the temporary filling and the gutta-percha most likely represent?

Between endodontic appointments a cotton pellet is commonly placed over the gutta-percha beneath the temporary restoration; it appears radiolucent on the radiograph.Other options: Internal resorption balloons the canal; recurrent caries is at margins; composite would not sit as a discrete radiolucent layer over fresh gutta-percha after one week.Key exam takeaway: A radiolucent layer between a temporary filling and gutta-percha = cotton pellet.