Looking at a full mouth series of radiographs you note that an impacted retained primary root tip can be observed between the right mandibular second premolar and the first molar in the premolar periapical radiograph

You note that the root tip appears to have "moved" mesially in the molar periapical radiograph. Which of the following is true regarding the impacted retained primary root tip?
a. It is located on the buccal.
b. It is located on the lingual.
c. An additional radiograph would be required to determine the buccal or lingual location of the impacted retained primary root tip.

a. If a full mouth series of radiographs is available and the object in question is imaged in more than one radiograph, it is possible to apply the tube-shift method when reading the radiographs to determine the buccal or lingual location of the object. This object moved in the opposite direction of the shift of the tube, so the object is located on the buccal.