Analysis Of The Three-dimensional Images Of Impacted Maxillary Canines And Root Resorption Of Adjacent Teeth

Objectives To evaluate the impacted maxillary canines and the root resorption of adjacent teeth using cone-beam computed tomography(CBCT)and three-dimensional image reconstruction technology,and examine whether there is a relationship between these and the age of patients.Materials and Methods Based on the inclusive standards,50 patients(19 male,31 female)who received orthodontic treatment at Dalian Stomatological Hospital with impacted maxillary canines were selected,aged 9 to 23 years old(mean age,14.04 years).They were categorized by age into two groups.Group A(16 cases)contained everyone under age12(including age 12)and Group B(34 cases)included everyone above age 12.They were scanned by the same CBCT machine(Ka Vo 3D e Xam;Imaging Scionces International,USA)before treatment.Then applied Invivo Dental 5.2 software to reconstruct and analyze the impacted maxillary canines and the root resorption of adjacent teeth,then recorded them.We recorded the following measurements : in the established three-dimensional system,the distance from the cusp tip of the impacted maxillary canine to X plane,Y plane,Z plane respectively and the distance from the cusp tip of the canine which erupted normally on the other side to X plane,Y plane,Z plane respectively;in any plane,the minimum distance between the impacted maxillary canine and adjacent central incisor,lateral incisor,bicuspid respectively;on panoramic radiography,the canine inclination to the midline(A angle),the canine inclination to the axis of the lateral incisor(B angle)and the canine inclination to the extended line of the occlusal plane(C angle);combined with sagittal,coronal and axial view,observing the root resorption of adjacent teeth and the degree of root resorption.Finally,statistical analysis was performed using SPSS Windows version24.0 software and used independent sample t test.The level of statistical significance was set at 5%.Results1)In the transverse plane,most of the impacted canines were located mesially(89.5%).In the sagittal plane,labial impacted canines were more common(70.2%).2)48.7% of adjacent teeth which were in contact with the impacted maxillary canines showed various degrees of root resorption,but there was no root resorption of contactless adjacent teeth.The most affected teeth were the lateral incisors(57.9%)followed by central incisors(31.6%),and the root resorption of bicuspids was unusual(10.5%).3)In the established three-dimensional system,the value of X,Y and Z had no significant correlation with the root resorption of adjacent teeth(P>0.05).4)On panoramic radiography,bigger the value of B angle was,easier the root of adjacent teeth resorbed(P<0.05).In contrast,smaller the value of C angle was,easier the root of adjacent teeth resorbed(P<0.05).But there was no significant correlation between the value of A angle and the root resorption of adjacent teeth(P>0.05).5)Root resorption of adjacent teeth showed a high significant association with the age of patients(P<0.05).The risk of root resorption increased with age,and the canine impacted more severely in the transverse and sagittal plane(P<0.05).But there was no significant correlation between the age of patients and the value of Z,A angle,B angle and C angle(P>0.05).Conclusions CBCT allows three-dimensional evaluation of an impacted canine to provide accurate information for diagnosis,treatment and surgical exposure.On panoramic radiography,bigger the value of B angle was,easier the root of adjacent teeth resorbed.In contrast,smaller the value of C angle was,easier the root of adjacent teeth resorbed.The degree of impacted canines and the risk of the root resorption of adjacent teeth both increased with age,which made the treatment more difficult.This indicated that the cases of impacted maxillary canines should be treated early.