Is the Etiology Behind Palatal Unilateral and Palatal Bilateral Maxillary Canine Ectopia Different?

The purpose of this study is to elucidate whether dentitions and craniofacial profiles are different in unilateral and bilateral maxillary canine ectopia.
Radiographic materials from 75 patients with non-syndromic palatally displaced maxillary canines were studied. Bilateral ectopia occurred in 37 patients and unilateral ectopia in 38 patients. Orthopantomograms were analyzed for dental deviation including taurodontic morphology, abnormal crown morphology, invaginations of the incisors and short root lengths. Skeletal morphology was studied cephalometrically according to Björk. Statistic analysis were included.
Significant more females than males had palatally ectopic maxillary canines. Gender differences were not observed between the uni- and bilateral ectopia groups. Orthopantomograms: the occurrence of taurodontia was significantly higher in the bilateral group while invaginations were significantly higher in the unilateral group. Patients with palatally displaced maxillary canines had an increased occurrence of agenesis. Profile radiographs: in the unilateral group significantly retroclined maxillary incisors in females and males and a significantly posterior inclined maxilla in females occurred. In the bilateral group a significantly reduced slope of the maxillary incisors was demonstrated. Compared to the individuals without palatally displaced maxillary canines, the maxillary incisors were significantly retroclined in both groups.
The present paper indicates a difference in the dentition and craniofacial profile in palatal unilateral and palatal bilateral maxillary canine ectopia. It is presumed that the unilaterally displaced canines have a dental origin while the bilateral cases have a skeletal origin. If this is so, the diagnosis of the dental morphology (invagination and taurodontia) might help to distinguish between cases with dental etiology and cases with skeletal etiology. This distinguish may improve orthodontic treatment.