Localising maxillary canines using dental panoramic tomography

Impacted maxillary canine teeth occur in about 2% of the population. Late detection of palatal canines may have treatment implications for the patient and medicolegal implications for the dental practitioner. Dental panoramic tomograms (DPT) are widely taken in practice. Image formation in dental panoramic tomography results in relative magnification of objects placed palatal to the image layer and relative diminution of objects buccal to it. This provides a possible means of bucco-palatal localisation of teeth. The aim of this study was assess the validity of DPTs in locating ectopic canines using the vertex occlusal view (VO) as the gold standard. One hundred pairs of radiographs showing 139 ectopic canines were examined. Using the DPT, it was possible to accurately predict the position of a palatally displaced crown in about 80% of cases. The DPT alone is not sufficient for canine localisation, but clinical evidence and suggestion of ectopic positioning on a DPT should warrant further radiographic investigation. Careful interpretation of a radiograph widely used in practice may lead to earlier detection of palatal canines.