The hypothesis that palatally displaced canines are associated with smaller than average lateral incisors with reduction of the root or tooth length, or with congenital absence of the adjacent lateral incisor was tested on a West of Scotland population. A retrospective study of the records of orthodontic patients attending Glasgow Dental Hospital was carried out. The palatal position of the canine was confirmed radiographically, or if erupted, on study casts. The tooth length of lateral and central incisors was measured on radiographs; the crown widths of lateral incisors was measured on study casts. An association was sought between the size of the lateral incisor or its absence, the position of the adjacent maxillary canine, and between crown size and tooth length of the lateral incisors. A separate study of extracted lateral incisors was undertaken further to test the hypothesis that narrow crowned lateral incisors have shorter roots than those with normally sized crowns. The conclusions supported the hypothesis that palatally displaced maxillary canines are associated with lateral incisors of smaller than average crown width. There was weak support for the association between palatal canines and absence of the adjacent lateral incisor, or between lateral incisor crown width and tooth length
