Reliability of a method for the localization of displaced maxillary canines using a single panoramic radiograph

The present study was initiated to determine the validity and reproducibility of a method previously reported for localization of displaced maxillary canines by panoramic radiographs. Eleven dental specialists (five orthodontists, five surgeons, and one radiologist) and five (final year) dental students were asked to interpret initial panoramic radiographs of 20 patients with 26 unerupted canines. The method contends that, provided that the radiographic image of the unerupted canines superimposes on the root of the lateral incisor at a height coronal to the apical third, a ratio between the widest mesiodistal dimension of the affected canine and the homolateral central incisor [Canine-Incisor Index (CII)] of more than 1.15 indicates palatal displacement. Among the observers, the measurement error was small, insufficient to cause overlap between the ranges of values for the CII of buccal and palatal canines. Inter-observer reproducibility was high. Without exception, all observers correctly diagnosed the location of each of the impacted canines. The CII cut-off point of 1.15, which was arbitrarily chosen in the previous work, was shown to be valid to differentiate buccal from palatal displacement. The present method is rapid, simple, accurate, and easily taught to dental students or dental specialists, with the simplest of initial instruction. While confirmations with other radiographic techniques is strongly advised before a definitive treatment is undertaken, this method has merit in providing more information than has been available from the panoramic radiograph hitherto, to satisfy the needs of an initial orthodontic consultation.