|Year : 2014 | Volume
| Issue : 1 | Page : 2-7
Evaluation of diagnostically difficult impacted maxillary canines in orthodontic patients and its effect on the root of adjacent teeth using cone beam computed tomography
Zahra Dalili Kajan1, Ali Khalighi Sigaroudi2, Navid Karimi Nasab3, Zhaleh Shafiee1, Somayeh Nemati1
1 Department of Maxillofacial Radiology, Guilan University of Medical Sciences, Dental School, Rasht, Iran
2 Department of Maxillofacial Surgery, Guilan University of Medical Sciences, Dental School, Rasht, Iran
3 Department of Orthodontics, Guilan University of Medical Sciences, Dental School, Rasht, Iran
|Date of Web Publication||2-Jun-2014|
Zahra Dalili Kajan
The end of professor Samii Blv, Guilan University of Medical Sciences, Faculty of Dentistry, Department of Maxillofacial Radiology, Rasht
Source of Support: None, Conflict of Interest: None
Purpose: To evaluate the morphology of apical portion of impacted maxillary canines and their effects on root resorption of adjacent teeth as well as their locations and inclinations with cone beam computed tomography (CBCT) in an individual group of orthodontic patients. Materials and Methods: In this descriptive cross-sectional study, 71 diagnostically difficult impacted canines of 55 orthodontic patients were studied with CBCT images. In this group, the orthodontic treatment approaches for eruption of their impacted teeth were not successful. A radiologist opined about the angulation, the position of apical and coronal portion of maxillary canine tooth, resorption of adjacent teeth as well as existence of apical hook and root curvature in reconstructed images. The simultaneous existence of hook and root resorption with other data was subjected to statistical analysis by Chi-square and Fisher's Exact tests. Results: In this cross-sectional study, the position of crown in buccopalatal dimension were respectively 16.9, 73.2 and 9.9% in buccal, palatal and middle portion of the alveolar bone. Apical hook was seen in 28.2% of cases. Root resorption of the adjacent teeth was induced in 32.3% of the cases, 69.6% of which were slight. Overall, there were no significant statistical differences between the presence of hook, and the positions and angulations of impacted teeth. Conclusions: Apical and palatal positions of crowns of the impacted maxillary canines were the most common locations in the selected groups. The possibility of root resorption of adjacent teeth could be related to angulation of impacted tooth.
Keywords: Cone beam computed tomography, impacted tooth, root resorption
|How to cite this article:|
Kajan ZD, Sigaroudi AK, Nasab NK, Shafiee Z, Nemati S. Evaluation of diagnostically difficult impacted maxillary canines in orthodontic patients and its effect on the root of adjacent teeth using cone beam computed tomography. J Oral Maxillofac Radiol 2014;2:2-7
|How to cite this URL:|
Kajan ZD, Sigaroudi AK, Nasab NK, Shafiee Z, Nemati S. Evaluation of diagnostically difficult impacted maxillary canines in orthodontic patients and its effect on the root of adjacent teeth using cone beam computed tomography. J Oral Maxillofac Radiol [serial online] 2014 [cited 2019 Dec 7];2:2-7. Available from: http://www.joomr.org/text.asp?2014/2/1/2/133544
| Introduction|| |
The main values of canine tooth are its long root, excellent bone support, its special shape, and relatively resistant to dental decay and periodontal diseases. These characters give canine a stabilizing effect against occlusal forces. These teeth endure main part of occlusal forces while mastication. Highly developed proprioceptive ability of canines help in retaining the residual teeth and results in longer survive of teeth. 
Absence of canine, due to impaction, extraction or congenital causes reduces the aesthetic of dental arch and facial harmony. On the other hand, loose contact between lateral incisor and the first premolar can be a focus of inflammation and food impaction. However, the efficacy of masticatory system will be reduced without the feasibility of tolerating the main forces. 
Among all teeth, canines have the longest time for development, the deepest developmental area and the most complex moving path from its origin to reach a complete occlusion. This makes the canines susceptible to wanted or unwanted environmental influences.  Maxillary canines are the most prevalent impacted teeth that have second frequency to the third molars.
The impaction of canines is more prevalent in females than males and 20 times more prevalent in maxilla than mandible. Palatal impaction is three times more prevalent than buccal impaction. In European population, palatally located impacted canine was at least two to three times more than labially ones. In Asian population, impaction was reported mostly labial or in middle alveolar. The ratio of Europeans to Asians for palatal position of the maxillary canines was reported 5:1. ,,,
Perception of the exact position of impacted canine, especially during the surgical procedure for exposing the canine may lead to a less invasive approach. Also the prognosis of impacted canine depends on awareness of its exact position. 
Root resorption of the adjacent incisors is the most common undesirable effects of the impacted canines.  The mechanism of root resorption following improper eruption pathway and the participating factors are not known. Most authors considered that the physical pressure during the eruption of maxillary canines is responsible for root resorption. 
Cephalometric and panoramic radiographs are commonly not precise in evaluation of longitudinal axis of impacted canine and its relation to the adjacent structures such as teeth and alveolar bone due to the overlap of structures on each other.  In addition, these images are not accurate for evaluation of root resorptions of lateral incisors especially in mild and early stages. 
In recent centuries, CBCT applied in different fields of dentistry such as implants planning, , assessing of mandibular third molars, ,, of temporomandibular joint , and examination of facial structures for orthodontic treatment. , CBCT generates images with higher special resolution and shorter exposure time than conventional CT. 
Based on a systemic review done by DeVos, et al. most clinical use of CBCT was in pre-treatment assessment of impacted teeth. 
Some orthodontists complain the difficulties of evaluation and alignment of impacted maxillary canines. Sometimes, routine radiographic and clinical investigations could not give explanation for the failures in treatment.
Considering the importance of the evaluation of the impacted tooth location and its effect on adjacent teeth as well as the effect of apical form of root on the prognosis of surgical and orthodontic treatment, this study was run to assess the positions of impacted canines as well as the morphology of apical portion and their effect on roots of adjacent teeth in three-dimensional CBCT images in limited number of patients with difficulties in diagnosis and/or orthodontic treatment.
| Materials and Methods|| |
In this cross sectional study, 55 orthodontic patients who needed CBCT scan from maxilla for evaluation and localization of impacted maxillary canines were selected in this study. All patients that the orthodontic treatment approaches for eruption of their impacted teeth were not successful and the routine methods of localization such as conventional radiographs and clinical exams were not enough to give reasons for the failure of the treatment and their localization were included in this study. Overall, 71 impacted maxillary canines were evaluated in this study. The CBCT images for all patients were obtained using New Tom VG equipment (QR Srl Company, Verona, Italy) in standard zoom mode at 110 KV, 5.4 Sec and 5.5 mA. Field of view (FoV) of selected mode was 4 Inch.
We originally obtained the ethics approval of this research by the ethics committee of the Dental School of Guilan University of Medical Sciences in Rasht, Iran before beginning this investigation (Ethics Approval Number 1339). The written consent of the patients was also obtained prior to initiating the study for using their CBCT scans data. The demographic information of patients such as age and sex were filled in provided form.
For reconstruction of study images from the volumetric image data, the reconstructed plane was selected parallel to the occlusal plan of maxilla. Axial images with a thickness and distance of 1 mm were prepared.
In the NNT viewer software of the NewTom VG CBCT machine, panoramic image with a 12 mm slice thickness was reconstructed. Besides, cross-sectional images with a thickness of 1 mm and an interval of 2 mm perpendicular to the mesiodistal and buccopalatal axes of impacted canines were prepared. After reconstruction of the images of the study, an expert maxillofacial radiologist with more than 15-years professional work experience opined about the angulation of crown as mesial, distal, vertical and horizontal position in reconstructed panoramic image. In cross-sectional images, the positions of apical and coronal portion of the maxillary canines were defined in buccopalatal dimension as buccal, palatal and middle alveolar position (and the position of crown in apico-coronal dimension as apical, middle and coronal position in relation to root of adjacent tooth. The positions of apical portion of impacted teeth were categorized as adjacent to maxillary sinus, adjacent to nasal cavity, in inverted Y region and in apical zone of premolars by observer [Figure 1]. Root resorption of adjacent teeth was assessed in axial and cross-sectional images based on Ericson et al.,  scores [Figure 2]. Root resorption was scored as mild, moderate, severe and without resorption. In the reconstructed three-dimensional images, the presence of hook [Figure 3] and the direction of root curvature (without curvature, mesial, distal, buccal and palatal) were determined. The frequency of each radiographic finding was reported. The possibility of the simultaneous incidence of the presence of hook and root resorption with other above mentioned findings were performed using the Statistical Package for Social Sciences (SPSS) Version 16.0 for Windows (SPSS: Chicago, USA) with statistical tests such as Fisher's exact and Chi-Square tests. P-values ≤0.05 were considered statistically significant.
|Figure 1: The position of apical third of left maxillary impacted canine in the zone of inverted Y|
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|Figure 2: Root resorption of left Lateral maxillary tooth by the crown of maxillary impacted canine|
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|Figure 3: The presence of apical hook of impacted maxillary canine in three dimensional CBCT image|
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| Results|| |
The study sample consisted of 71 impacted maxillary canines from 55 diagnostically difficult patients (5 males and 50 females) having an average age of 22.85 years, ranging from 10 to 52 years. Bilateral canine impaction was seen in 16 patients and 39 patients had the unilateral type. Considering the location, 22 cases of 39 unilateral impacted canines were on the left side and 17 cases were on the right. Overall, 33 (46.5%) of impacted canines were on the right side and 38 (53.5%) were on the left.
The position and angulation of the crowns of impacted canines and also the position of the roots in CBCT images are shown in [Table 1] and [Table 2]. Position of apex in relation to buccal cortex, medial wall of maxillary sinus (MS), Nasal Cavity (NC), Inverted Y (Inv Y) and apex of premolars were assessed. The most and the least frequent location of apical portion of impacted canines were in inverted Y (42.3%) and adjacent to apex of premolars (4.2%), respectively.
|Table 1: The frequency of position and angulation of impacted maxillary canines|
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|Table 2: Distribution of different positions of apex in|
relation to buccal cortex
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Apical hook was found in 28.2% of samples. Root curvature was detected in 39 subjects (54.9%) that were toward buccal (8.5%), palatal (23.9%) and mesial (22.5%) directions. Distal direction of apical root curvature was not found. Root resorption of adjacent teeth, its severity and its relation to position and angulation of crown of impacted teeth are shown in [Table 3] and [Table 4].
|Table 3: Distribution of root resorption in adjacent teeth and its severity|
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|Table 4: Distribution of root resorption of adjacent teeth in different positions and angulations of the crown|
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A significant difference was detected between the different angles of impacted canines in CBCT images and root resorption of adjacent teeth. However, root resorption of adjacent teeth was found most frequently in horizontal position (50%) and the least in vertical position (5.9%) [Table 4].
Significant differences did not exist between the presence of apical hook among the different positions of crowns and roots of impacted canines while there was a clinical difference in the frequency of apical hook among different angles of impacted canines [Table 5].
|Table 5: Apical hook in different positions and angulations of the crown of impacted maxillary canines|
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| Discussion|| |
The maxillary canine is a cornerstone of dental arch and its role in occlusion and lateral movements of mandible is well known.  Stivaros et al.,  reported palatally and labially located impacted canines were observed in 61% and 5% of patients, respectively, and in the remaining of cases; the position was in situ (34%). Rimes et al.,  studied on 32 impacted canines and reported 14 cases in palatal position.
Szarmach et al.,  in a study on 102 impacted canines found the most frequent location was in palatal side (67%). In another study on CT diagnosis of 113 impacted canines, 42% were in palatal and 40% were in buccal side.,  Liu et al.,  reported the impacted canines 41% were located palatally, 45% labially and 14% middle alveolarly in CBCT images.
In our study, the prevalence of palatal, middle and buccal position of maxillary impacted canines with specific criteria was 73.2, 9.9 and 16.9%, respectively, which was in accordance with the results of several studies. ,,
In this study, in apico-coronal dimension, the crowns of impacted teeth located in apical (38%), coronal (35.2%) and middle (26.8%) area orderly. While Sudhakar et al. reported the crowns of impacted teeth, 32% in apical, 39.3% in middle and 28.7% in coronal region.  We consider that the difficult treated impacted maxillary canines have a tendency to be located apically.
The crowns of impacted canines were positioned 66, 23.9 and 14.1% in mesial, vertical and horizontal directions, respectively. Liu et al. reported 67.1, 14.8, 5.7, 8.6, and 3.8% of the cases to be oriented mesially, in situ (same as vertical orientation in this study), distally, horizontally and reverse, respectively. 
Apical hook was found in 28.2% of subjects in our investigation. The root curvature in 54.9% of cases was detected. The most and least common apical curvature was determined respectively in palatal (23.9%) and buccal orientations. Buccal tendency (52.1%) of apical third of root was more than other locations.
In this study, the most common position of the apical third of maxillary impacted canines was found in inverted Y region but there were no similar studies for comparison.
In a study done by Liu et al. on 210 impacted canines, resorption rate of lateral incisor and central incisor reported to be 27.2 and 23.4%, respectively.  The mild root resorption was detected in 49 impacted canines and severe form was only defined in 23 of cases. Sasakura and co-workers found only 1 out of 11 patients with three resorbed incisors and did not find any patients with four resorbed incisors.  In addition, Ericson and Kurol  did not detect any cases with four resorbed incisors. In their study, only 3 out of 41 patients had bilateral resorption of lateral incisors. Rimes et al. studied on 26 patients who had root resorption of 26 lateral and 9 central incisors.  However, eight of resorbed teeth were involved bilaterally. Though Szharmach et al. study on 82 patients with impacted canines found that root resorption of lateral incisors was detected only in five patients that four of them were bilateral.  They also confirmed that tomography is reliable method in diagnosis of root resorption. Using CT, Eriscson and Kurol observed that only 7 cases of 167 canines resulted in resorption of both lateral and central incisors.  In our study 23 cases (32.3%) of 71 impacted canines resulted in resorption of adjacent teeth which is less than the result of Liu et al.  study. Eleven of 24 teeth with root resorption were lateral incisors. Seven central incisors and 4 deciduous canine teeth had root resorption. Simultaneous resorption of lateral and central incisor was found in 1 case. The severity of root resorption was mild in 16 samples, moderate in 2 and severe in 5 cases.
In this study, there was a relation between root resorption of adjacent teeth and different angulations of studied subjects. Root resorption of adjacent teeth was seen mostly in horizontal position (50%) and the least in vertical position (5.9%). In Liu et al. study, 65 cases with resorption of incisors were found in relation to 75 impacted canines which were located mesially in central incisor region (86.7%), only 34 incisors (42%) were resorbed that related to 81 impacted canines located in lateral incisor region or between lateral and central incisors.  Other 6 incisor resorptions were happened adjacent to 35 impacted canines which were positioned in situ.
Also, there was no significant statistical difference between different positions of crowns and roots, and also angulation of impacted maxillary canines with the presence of apical hook. The ability of root resorption of adjacent roots is only related to tooth angulation and is more common in horizontally angulated impacted canines.
| Conclusion|| |
Apical and palatal positions of crowns of this group of the impacted maxillary canines were the most common location. The frequency of the presence of hook was highest in horizontal position of impacted maxillary canine thus before orthodontic treatment the evaluation of apical portion of this group of impacted teeth should be considered. There were no statistical relation between different positions and angulations of canines and the presence of apical hook. The positions of impacted canine could be effective on the ability of the root resorption of adjacent teeth. Apical root curvature and hook could be risk factor for failure of orthodontic treatment.
| Acknowledgment|| |
I would like to express my gratitude to the Vice Chancellor of Research and Technology of dental school, Guilan University of Medical Sciences to approve this research.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]