The maxillary permanent canine is the most frequently impacted tooth after the third molar. The prevalence of impaction is 0.9%-3.0%, and it is twice as common in females than in males. The position of impacted canines reported by different authors varies, but in most studies, the canines are located palatally (41%-90%). The exact etiology of this abnormality is unknown. Genetic and local predisposing factors such as congenitally missing lateral incisors, supernumerary teeth, odontomas, and other conditions that interfere with the eruption path of the canine, have been implicated. Early diagnosis of the impaction greatly improves the prognosis of orthodontic treatment because the early therapeutic interference eliminates or minimizes complications of the impaction. The most important complications are the following: (1) migration of the neighboring teeth, (2) loss of arch length, (3) cysts, (4) infections, (5) root resorption, (6) necrosis of the adjacent lateral or central incisor, and (7) ankylosis and pain caused by the unerupted canines. Clinical diagnosis is very difficult because of the lack of symptoms in most cases. For this reason, canine impaction may cause severe problems that will further complicate orthodontic treatment.

Root resorption of the maxillary incisors caused by impacted canines is a relatively common phenomenon. However, the incidence of this complication varies, and it depends on the radiographic method used for diagnosis. Using conventional imaging methods, Townend found 3 cases in 3000 patients over a 3-year period, whereas Ericson and Kurol found that 12.5% of ectopic canine cases presented noticeable root resorption.

Resorption caused by impacted maxillary canines occurs more frequently in lateral rather than in central incisors. However, when computed tomography (CT) or cone-beam computed tomography (CBCT) scans were used, results appeared to differ between different researchers. Rimes et al found 74.2% of the lateral incisors demonstrated resorption in a total of 35 affected incisors. Ericson and Kurol in a CT study of 107 patients reported 80.5% lateral incisors with root resorption. Moreover, the results of a CBCT study by Walker et al are in accord with the previous studies because they found only 3 central incisors with resorption in a total of 21 involved incisors. In a later CBCT study, Liu et al examined 105 incisors with signs of resorption, and the results showed only a small difference between lateral (53.3%) and central incisor resorption (46.7%). However, in another project, resorption appeared more often in the central incisor area (52.2%) compared with the lateral.

Radiographic evaluation is always essential to confirm the canine impaction. Several methods have been used to accomplish this: occlusal and periapical projections, panoramic, posteroanterior or lateral cephalometric radiographs, and more advanced techniques, such as CT and CBCT. Among the diagnostic methods, the CBCT overcomes the limitations of 2 dimensional (D) techniques and gives more precise results. CBCT creates a 3D visualization of the dentition and the anatomical structures making the study of their relationship easier. The use of CBCT increases significantly the detection of root resorption by eliminating blurring and overlapping of other teeth. The sensitivity of CBCT compared with the conventional x-rays is much higher allowing accurate diagnosis of the location and the degree of resorptive cavities.

The purpose of this study was to examine the incidence and position of maxillary lateral and central incisor root resorption owing to the impaction of maxillary canines by means of CBCT and to investigate parameters associated with the respective resorption.