Localization of the unerupted maxillary canine: how to and when to

Reasons for localizing impacted maxillary canines are outlined and methods of localization described. The favored method of radiographic localization is the parallax method (image/tube shift method). Tube shifts can be carried out in both the horizontal and the vertical planes. For a horizontal tube shift, two occlusal radiographs are recommended; for a vertical tube shift, a rotational panoramic radiograph and an occlusal radiograph are recommended. This latter combination is usually the combination of choice because the panoramic radiograph, which provides information about all the teeth in both arches, the two jaws, and the surrounding structures, is often taken as an initial radiograph and this combination only requires one additional exposure, the occlusal radiograph. To facilitate the interpretation of a vertical tube shift, the angle of the tube in the occlusal radiograph should be increased from the customary 60 degrees to 65 degrees to 70 degrees to 75 degrees. Less accurate methods of radiographic localization are to use (1) image magnification of the impacted maxillary canines and (2) image superimposition of the impacted maxillary canines on the central or lateral incisor. Reasons why periapical radiographs are not recommended to be used for a horizontal tube shift or for a vertical tube shift in combination with a panoramic radiograph are explained. Indications to suspect palatal impaction may occur in the future if the patient is less than 10 years of age, and indications to suspect impaction may have occurred if the patient is more than 10 years of age are discussed. Patient questionnaires are advocated to aid the clinician in anticipating palatal impaction, the most frequent impaction.