The purpose of this study was to examine the incidence and position of lateral and central incisor root resorption owing to the impaction of maxillary canines by means of cone-beam computed tomography and to investigate parameters associated with the respective resorption.
Sixty-one patients presenting with unilateral or bilateral impacted maxillary canines were evaluated in a university clinic in Athens, Greece, using cone-beam computed tomography scan. No patient had undergone any type of orthodontic treatment in the past. Eleven different parameters related to the existence, grade, and localization of resorption were examined. Logistic regression analysis was used to evaluate potential associations.
In our study, canine impaction caused lateral root resorption in 18.5% of the cases examined. Age was associated with localization of the impacted maxillary left canine in a palatal-buccal direction. More specifically, in younger patients, the impacted left canine was more likely to be located in the middle of the maxillary bone, whereas in older patients, it was more likely to be located in the palatal or buccal side of the bone. Lateral root resorption in the apical or middle third was more common in the younger ages, whereas lateral root resorption in the incisal third more common in the older ages. Lateral root resorption increased as the angle between the longitudinal axis of the impacted canine and the adjacent lateral incisor also increased.
Incidence of lateral root resorption was 18.5% in this study population. In younger patients, the impacted canines appear more often in the middle of the maxillary bone, whereas in older patients, the canines are located more often in the palatal or buccal side of the maxilla.
Lateral incisor root resorption because of canine impaction was found in 18.5% of cases.
Younger subjects had resorption in the apical or middle third of the lateral’s root.
Older subjects had resorption at the incisal third of the lateral incisor root.
The angle between canine and lateral incisor is positively correlated with resorption.
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.
Material and methods
The study population was comprised of 61 patients with impacted canines seeking overall dental treatment between 2005 and 2010 at the School of Dentistry of the National and Kapodistrian University of Athens, Greece. The range of ages was from 9 to 57 years, and there were twice as many females as males (42 females and 19 males). None of them had undergone any form of orthodontic treatment in the past.
The CBCT technique was selected to identify more accurately the possibility and extent of resorption. Overall, 61 cone-beam tomographies of the maxilla from 61 different patients presenting unilateral or bilateral impacted maxillary canines were performed at the Radiology Department of the School of Dentistry. Thirty-one patients presented unilateral canine impaction whereas 30 patients’ bilateral impaction. All patients were examined using a NewTom QR-DVT 9000 device (QR s.r.I., Verona, Italy). Using radiographic information from the CBCT images, several different parameters were analyzed and measured:
Distance of the impacted canine tooth from the medial suture of the palate ( Fig 1 ).
Localization of impacted canine tooth in a palatal-buccal direction.
Determination of the angle of the longitudinal axis of the impacted tooth and the longitudinal axis of the lateral incisor tooth and the central incisor tooth of the ipsilateral side ( Fig 2 ).
Root resorption of the adjacent lateral incisor tooth at A, the level of the apex of the root; B, the median level of the root; and C, the incisal level of the root ( Fig 3 ).
Root resorption of the ipsilateral central incisor tooth at A, the level of the apex of the root; B. the median level of the root; and C, the incisal level of the root ( Fig 3 ). The Ericson and Kurol classification of root resorption severity was used for this measurement.
Existence of dental follicle of the impacted tooth.
Size of the dental follicle.
Coexistence of any tooth agenesis.
Logistic regression analysis was used to evaluate the potential association between resorption and studied parameters and the age of the sample. All statistical analyses were performed using Stata/SE statistical software (version 11.0; StataCorp, College Station, Tex). Statistical significance was set at the level of P <0.05.
The mean age of the sample was 22.5 years (range 9-57 years). A total of 42 impacted right canines and 49 impacted left canines were found. The age distribution demonstrated that most of the patients were between the ages of 9 and 14 ( Table I ). The average distance between the position of impacted canines in the maxilla and the suture was 4.21 mm ( Table II ; Fig 4 ).