Palatally impacted canines: A new 3-dimensional assessment of severity based on treatment objective.

Abstract

The severity of a palatally impacted canine (PIC) is gauged radiographically on 2-dimensional and 3-dimensional positional components: eg, angulation and height. We hypothesized that the position of a PIC relative to its virtual alignment in the arch is a better indication of impaction severity and treatment requirements. The aims of this research were to evaluate variations in PIC location on 3-dimensional images and to determine positional components associated with impaction severity. Linear and angular measurements of 38 PICs from 28 cone-beam computed tomography scans were made on the panoramic, coronal, sagittal, and axial sections. Measurements included angulation of the PIC to the virtually aligned canine, midline, and palatal plane; and distances between cusp tip and apex to various reference planes-eg, occlusal and midpalatal. Statistical assessments comprised t tests for group comparisons based on PIC and virtually aligned canine severity (cutoff at 30°) and Pearson product moment correlations for associations among variables. Angulations of the PIC to the virtually aligned canine were 32.5° ± 15.5° (range, 9°-59°) and 19.6°±6.9° and 45.37°±9.6°, respectively, in the less severe and more severe groups (P<0.001). Group differences were significant (0.023<P<0.001) for the apex and cusp distances between PICs and virtually aligned canines and to the midline reference planes, and for PIC angulations to the palatal plane and midline. Correlations were highest (0.7<r<0.9; P<0.001) among PIC angulations to virtually aligned canines and to midline planes (panoramic and coronal sections), and cusp to midline distances (panoramic and axial views). A novel measurement of PIC inclination to its virtual aligned position indicates medial inclination of the most severe PIC with the crown farther from the alveolar crest and the apex more posterior. The crown varied over a wider range in the transverse plane; the apex varied over a comparatively narrower track anteroposteriorly.