| Objective:The purpose of the study was to investigate the application of cone beam computed tomography (CBCT) in the diagnosis of the three-dimensional locations of impacted maxillary canines and root resorption of neighboring incisors, and to evaluate the validity of the panoramic tomography (PTG) in the diagnosis of impacted maxillary canines.Methods:1. Fifty-five patients (sixty-two impacted maxillary canines) were scaned by CBCT. Linear and angular from the impacted canines to the reference planes were measured, and the characteristics of the impacted canines with the different locations were compared.2. The extent and location with the root resorption of neighboring incisors were observed in the sequential transaxial views; Whether there were differences in the root resorption of incisors between the canines contact with the neighboring incisors group and non-exposed group was compared; Whether there were differences in the dental follicle width of the impacted canines between the root resorption of neighboring incisors group and non-exposed group was also compared.3. The labial-palatal angle (LPA) were calculated on PTG images via inverse trigonometric, then the LPA in the CBCT and PTG were compared. Taking the amount of root resorption on CBCT images as the standards, we calculated the sensitivity and specificity of the PTG.Results:1. The mesial-labial and mesial-palatal impactions account for 45.2%and 40.3% separately among all cases. In the distance from the cusp tip of the impacted canine to the occlusal plane and to the mid-sagitral plane and to the frontal plane, mesial and distal impaction groups showed statistically significance. In the distance from the cusp tip of the impacted canine to the occlusal plane and to the frontal plane, and in the angles from the impacted canine to the occlusal plane and to the frontal plane, mesial and distal impacted groups showed statistically significance.2. The percentage of lateral resorption (38.7%) was higher than that of central resorption (21.0%), and there was statistically significance (x2=4.66, P<0.05) The extent of incisors resorption were mainly mild resorption(45.9%) and moderate resorption(32.4%), and the location of incisors resorption were mainly in the middle 1/3(35.1%) and apical 1/3(37.8%) of the root. And 73.0%of these resorptions occurred where the impacted canines were in close contact with the incisors.3. The labial-palatal location of crown with the impacted maxillary canines showed statistically significance between PTG and CBCT (x2=9.30, P<0.01). The LPA of impacted maxillary canines showed no statistically significance between PTG and CBCT images (P>0.01). The sensitivity and specificity of diagnosing the incisors root resorption caused by impacted maxillary canines using PTG were 43.8%and 82.4%respectively. There was a low consistency (Kappa test, k=0.268<0.40) in diagnosing the incisors root resorption using PTG and CBCT.Conclusions:1. CBCT can accurately locate the impacted maxillary canines, and it can provide a reliable evidence for surgical and orthodontic treatment.2. The locations of impacted maxillary canines varied greatly, but a large of impacted maxillary canines were mesial-labially impacted and mesial-palatally impacted.3. The resorption of neighboring incisors, especially lateral incisors, occurred in a high rate. The extent of root resorption was mainly mild and moderate, and the root resorption was mainly located on the middle and apical thirds of the root.4. Root resorptions of neighboring incisors were significantly correlated with contact between the incisors and impacted canines, whereas they were not correlated with dental follicle width of the impacted canines.5. The reliability of positive diagnosis of incisors root resorption caused by impacted canines with PTG was low, and the reliability with CBCT was high. So CBCT should be widely applied in clinical. |
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