Abstract: Objective To establish a 3D image classification system for maxillary canine impactions based on spiral CT.Methods A retrospective sample of 102 subjects with maxillary canine impaction （121 impacted canines） were selected.All subjects received standard CT scans and all data （DICOM files） were reconstructed through MIMICS10.01 by the means of Surface Shaded Display （SSD） to show the 3D position of the impacted canines.Based on the analysis of 121 impacted canines,a 3D CT image classification system for maxillary canine impactions was established.Results A database for 3D CT images of different maxillary canine impactions was established.The data showed that the type of mesial cusp tip with normal root apex of maxillary canine was most common on the Xaxis while there were only three types on the Yaxis which were high root apex with high,middle or low cusp tip of maxillary canine.And the type of buccal cusp tip with buccal root apex of maxillary canine （about 1/3） was most common on the Zaxis.Conclusions A 3D image classification system for maxillary canine impactions based on spiral CT was established with certain diagnostic value.

Key words: impacted canine, spiral CT, classification, three dimensional