What complication can occur after internal (walking) bleaching of a non-vital tooth if the existing root canal filling at the cervical region is not properly sealed?

If the cervical seal of the root canal filling is inadequate during internal bleaching, the bleaching agent (commonly hydrogen peroxide-based) can seep into the periodontal ligament space at the cervical region, triggering an inflammatory response that can lead to cervical resorption — a well-documented, classic complication of this specific procedure.