Localization of paraoral soft tissue calcifications: the known object rule.

The interpretation of panoramic radiographs requires an understanding of the formation of real and ghost images in rotational panoramic radiology. This article illustrates the use of principles of interpretation in panoramic radiology to identify paraoral soft tissue calcifications, which appear as lesions in the third molar-ramus region of the mandible. The known object rule, a variation of the buccal object rule, is presented as an aid in identifying soft tissue calcifications of the region of the head and neck.