Triple images on panoramic radiographs.

OBJECTIVE: To explain the formation of triple images on panoramic radiographs. METHODS: A metal test object was placed in defined positions in relation to movement path of a panoramic X-ray beam. RESULTS: The test object was portrayed once, twice or three times with varying degrees of distortion depending on its location. Triple images were formed when the test object was located in a specific diamond-shaped area distal to the path of the rotation centre of the X-ray beam. CONCLUSIONS: The formation of triple images on panoramic radiographs can be explained on the basis of known projection geometry.