Three-dimensional evaluation of angular, linear, and resorption features of maxillary impacted canines on cone-beam computed tomography İlhan Metin Dağsuyu, Fatih Kahraman & Rıdvan Okşayan
Oral Radiology ISSN 0911-6028 Oral Radiol DOI 10.1007/s11282-017-0289-5
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Author's personal copy Oral Radiol DOI 10.1007/s11282-017-0289-5
ORIGINAL ARTICLE
Three-dimensional evaluation of angular, linear, and resorption features of maxillary impacted canines on cone-beam computed tomography I˙lhan Metin Dag˘suyu1 • Fatih Kahraman1 • Rıdvan Oks¸ ayan1
Received: 14 March 2017 / Accepted: 13 April 2017 Ó Japanese Society for Oral and Maxillofacial Radiology and Springer Japan 2017
Abstract Objectives The aim of this study was to evaluate the localization, angulation, and resorption features of maxillary impacted canines on cone-beam computed tomography (CBCT). Methods This retrospective study examined the CBCT scans of 140 maxillary impacted canines in 102 patients (43 males, 59 females; mean age: 16.25 ± 6.31 years). The following impacted canine-related parameters were analyzed on the CBCT images: impaction side; location; root resorption levels of adjacent teeth; occlusal plane and midline distances of impacted canines; and angulations of impacted canines to midline, lateral incisor, and occlusal plane. Results Bilateral canine impaction was found in 38 subjects, and unilateral canine impaction was present in 64 subjects. Severe resorption was found in 14 canines. There were no significant differences between the occlusal plane and midline distances to the impacted canine cusp tip and root apex (p [ 0.05). The midline angulation of right maxillary impacted canines was significantly higher than that of left maxillary impacted canines (p \ 0.05), while the occlusal plane angulation of left maxillary impacted canines was significantly higher than that of right maxillary impacted canines (p \ 0.05). Conclusions Maxillary canine impaction was more frequently seen in female subjects than in male subjects. Lateral incisors were more frequently affected than first premolars, and slight resorption was more frequently seen & Rıdvan Oks¸ ayan
[email protected] 1
Department of Orthodontics, Faculty of Dentistry, Eskis¸ ehir Osmangazi University, Eskis¸ ehir 26000, Turkey
in adjacent teeth. CBCT assessment of maxillary impacted canines can provide accurate measurements of angular, linear, and resorption parameters. Keywords Maxillary impacted canine Resorption CBCT
Introduction Maxillary canines have very important roles in facial and dental esthetics, occlusion development, and function. Permanent maxillary canine impaction is a common problem encountered in orthodontic clinics, with a prevalence rate of 1–5% and a higher rate of occurrence in female patients [1–3]. The etiology of maxillary impacted canines depends on many factors, including deciduous canine retention, crowding in upper arch, odontoma, and maxillary canine ankylosis [4]. Early and accurate detection of this problem is very important for treatment and resolution of adverse situations, as canine impaction can lead to many unwanted conditions, including resorption in adjacent teeth and cystic lesions [5, 6]. Effective placement of maxillary impacted canines in the dental arch through fixed orthodontic treatment is related to many factors, such as patient age, impacted canine location and angulation, and narrow maxillary arch [1, 7]. These factors are also important for extrusion placement onto the maxillary impacted canine surface during surgical procedures. Another situation that requires consideration during orthodontic treatment planning is the proximity of impacted canines to the roots of lateral incisors and premolars. In recent years, the techniques used to detect maxillary impacted canines have improved with new advances in
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medical imaging technologies. Two-dimensional images are error-prone and provide inadequate information for evaluation of impacted teeth. Cone-beam computed tomography (CBCT) is superior to conventional radiography, in that it supplies three-dimensional multiplanar images and information on dentofacial structures [8, 9]. Through the use of CBCT images, many unidentified features of impacted canines can be easily resolved. The aim of this study was to extensively examine the features of maxillary impacted canines (i.e., location, angulation, and resorption in adjacent teeth) on CBCT.
Materials and methods The study protocols were approved by the Eskis¸ ehir Osmangazi University Clinical Research Ethical Committee (80558721/G-131). The study subjects were referred to the Department of Orthodontics at Eskis¸ ehir Osmangazi University Faculty of Dentistry for consultation and treatment of maxillary impacted canines. The CBCT images of 140 bilateral or unilateral impacted canines in 102 subjects (43 males, 59 females; mean age: 16.25 ± 6.31 years) were retrospectively examined in this study. We defined any case as maxillary canine impaction if the root formation was complete or the other side of the maxillary canine had completely erupted [10]. All patients were nonsyndromic, had no systemic disease related to bone, and presented with at least one maxillary impacted canine. In addition, no subjects had previously undergone orthodontic treatment, and all subjects had late mixed dentition (dental age of [12 years). All CBCT images were obtained in the standing position using a Promax 3D Mid machine (Planmeca, Helsinki, Fig. 1 Maxillary impacted canine angulations to the midline and lateral incisor were measured on CBCT images in the coronal plane
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Finland). The exposure parameters were 94 kVp, 14 mA, and 27 s. The CBCT images were evaluated in all three planes (sagittal, axial, and coronal) on a flatscreen monitor by a single orthodontist with 7 years of experience. The CBCT image software Simplant O&O (Materialise, Leuven, Belgium) was used for image evaluation. The patient background characteristics (age, sex) were recorded. The following impacted canine-related variables were analyzed on the CBCT images: impaction side (bilateral or unilateral); location (buccal, central, or palatal); root resorption levels and numbers of adjacent teeth (right and left lateral incisors and premolars); occlusal plane and midline distances to maxillary impacted canine crown tip and apex; and angulations of impacted canines to midline, lateral incisor, and occlusal plane. Resorption was evaluated on the right and left lateral incisors and first premolars. A resorption degree of 1–4 was assigned as previously described [11]: degree 1, no resorption; degree 2, slight resorption (up to one-half of dentin thickness); degree 3, moderate resorption (midway or more to pulp, but pulp covered with unbroken dentin); and degree 4, severe resorption with exposed pulp. The maxillary impacted canine angulation to the midline was evaluated in the coronal plane, between the long axis of the maxillary impacted canine and the maxillary arch midline. The angulation to the lateral incisor was also evaluated in the coronal plane, but between the long axis of the maxillary impacted canine and the lateral incisor [1]. The maxillary impacted canine angulation to the occlusal plane was measured between the occlusal plane and the long axis of the maxillary impacted canine, in the sagittal plane (Figs. 1, 2). The occlusal plane distances to the impacted canine cusp tip and root apex were evaluated on a perpendicular
Author's personal copy Oral Radiol Fig. 2 Maxillary impacted canine angulations to the occlusal plane and canine cusp tip and apex distances to the occlusal plane were measured on CBCT images in the sagittal plane
for independent samples was used to analyze the relationships among parameters. All statistical analyses were performed at the 5% significance level.
Results
Fig. 3 Maxillary impacted canine cusp tip and apex distances to the midline were measured on CBCT images in the axial plane
line in the sagittal plane. The maxillary midline distances to the impacted canine cusp tip and root apex were measured on a perpendicular line in the axial plane (Figs. 2, 3). Statistical analyses were performed using Excel software (Microsoft Corp., Redmond, WA, USA) and MedCalc Software for Windows v17.1 (Broekstraat, Mariakerke, Belgium). All linear, angular, and resorption measurements were repeated in 20 randomly selected samples after 30 days by the same investigator. The Pearson correlation test was used to examine the differences between the measurements at these two time points (Pearson correlation coefficients: 0.890 for linear measurements, 0.918 for angular measurements, and 0.923 for resorption degree measurements). The Kolmogorov–Smirnov test was used to evaluate normality, and Student’s t test
In this retrospective study, a total of 140 maxillary impacted canines in 102 patients were analyzed on CBCT images. As mentioned earlier, the 102 patients comprised 43 males (42.1%) and 59 females (57.9%). Seventy-two (32 male, 40 female) maxillary impacted canines were located on the right side and 68 (27 male, 41 female) maxillary impacted canines were located on the left side. Bilateral maxillary canine impaction was found in 38 (16 male, 22 female) subjects, and unilateral impaction was present in 64 (27 male, 37 female) subjects (Table 1). As shown in Table 2, maxillary impacted canines were most frequently located palatally (54.3%), followed by centrally (27.8%) and buccally (17.8%). Regarding root resorption in adjacent teeth, 144 (72 lateral incisor, 72 first premolar) right teeth and 136 (68 lateral incisor, 68 first premolar) left teeth were evaluated (Fig. 4). The data for resorption are shown in Table 3. Among the right lateral incisors, 44.44% showed no resorption (degree 1), 38.88% slight resorption (degree 2), 8.33% moderate resorption (degree 3), and 8.33% severe resorption (degree 4). Among the right first premolars, 72.22% showed no resorption (degree 1), 19.44% slight resorption (degree 2), 5.55% moderate resorption (degree 3), and 2.77% severe resorption (degree 4). Among the left lateral incisors, 45.58% showed no resorption (degree 1), 35.29% slight resorption (degree 2), 13.23% moderate resorption (degree 3), and 5.88% severe resorption (degree
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Author's personal copy Oral Radiol Table 1 Patients’ characteristics (age, sex, features)
Variables
Male
Female
Total
Patients
43 (42.1%)
59 (57.9%)
102 (100%)
Age
15.54 ± 6.6
16.8 ± 6.1
16.25 ± 6.31
Patients with unilateral impaction
27 (42.1%)
37 (57.9%)
64 (100%)
Patients with bilateral impaction
16 (42.2%)
22 (57.8%)
38 (100%)
Left side
27 (39.7%)
41 (60.3%)
68 (100%)
Right side
32 (44.4%)
40 (55.6%)
72 (100%)
Total impacted canines
59 (42.1%)
81 (57.9%)
140 (100%)
Table 2 Locations of maxillary impacted canines according to sex Sex
Buccal maxillary canine impaction
Male
16 (27.1%)
18 (30.5%)
25 (42.4%)
59 (100%)
9 (11.1%)
21 (25.9%)
51 (63.0%)
81 (100%)
Female
Central maxillary canine impaction
Palatal maxillary canine impaction
Total
Fig. 4 Axial CBCT images showing maxillary impacted canines causing root resorption of degree 1 (a), degree 2 (b), degree 3 (c), and degree 4 (d) in the adjacent teeth
4). Finally, among the left first premolars, 82.35% showed no resorption (degree 1), 8.82% slight resorption (degree 2), 5.88% moderate resorption (degree 3), and 2.94% severe resorption (degree 4). No significant differences were observed for the distances of the occlusal plane and maxillary midline to the impacted canine cusp tip and root apex between the right and left sides (p [ 0.05; Table 4). However, significant differences were found between the left and right sides for the angulations of the impacted canines to the midline and occlusal plane (Table 5). Specifically, the midline angulation of right maxillary impacted canines was significantly higher than that of left maxillary impacted canines (p \ 0.05), while the occlusal plane angulation of left maxillary impacted canines was significantly higher than that of right maxillary impacted canines (p \ 0.05).
Discussion A variety of orthodontic treatment alternatives, such as extraction, prevention, or active therapy, have been considered for maxillary impacted canines, depending on the presence of resorption in the adjacent teeth, and the angulation and location of the maxillary impacted canines,
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as well as patient age, malocclusion, and pathologies in surrounding tissues [12]. In such situations, evaluation of maxillary impacted canine angulation, location, and surrounding structures on CBCT images is very valuable for administering fixed orthodontic treatments. Many factors can affect conventional radiographic images and are dependent on the patient position in the imaging process, the radiological methods used, and the limitations inherent in working with the crowded anterior maxillary region [13]. Serrant et al. [14] found that CBCT was more accurate than either vertical or horizontal parallax in the localization of ectopic maxillary canines. Furthermore, CBCT was reported to accurately obtain three-dimensional multiplanar images of teeth and surrounding structures in the maxillary impacted canine region [15]. Bjerklin et al. [16] examined how use of CT in examinations can change orthodontic treatment plans in cases with maxillary impacted canines, finding that 44% of the total orthodontic treatment plans studied were changed after undertaking CT evaluations. In the present study, we found that the majority of our patients with maxillary canine impaction were female (57.9%). Consistent with this finding, Lai et al. [9] reported a female-to-male ratio of 2:1 in a maxillary impacted canine study. In addition, Warford et al. [17] found that
Author's personal copy Oral Radiol Table 3 Resorption levels and numbers of right and left lateral incisors and first premolars with resorption because of maxillary impacted canines Resorption degree
Right lateral incisor
Right first premolar
Left lateral incisor
Left first premolar
Degree 1 (none)
32 (44.44%)
52 (72.22%)
31 (45.58%)
56 (82.35%)
Degree 2 (slight)
28 (38.88%)
14 (19.44%)
24 (35.29%)
6 (8.82%)
Degree 3 (moderate)
6 (8.33%)
4 (5.55%)
9 (13.23%)
4 (5.88%)
Degree 4 (severe)
6 (8.33%)
2 (2.77%)
4 (5.88%)
2 (2.94%)
Table 4 Comparisons of right and left impacted canine crown and apex distances to the occlusal plane and midline Variables (mm)
Right side (n = 72)
Occlusal plane distance to impacted canine crown tip (mean ± SD)
10.02 ± 3.75
9.96 ± 3.52
0.597
Occlusal plane distance to impacted canine apex (mean ± SD)
26.99 ± 4.56
27.22 ± 4.39
0.765
9.41 ± 5.00
9.21 ± 5.37
0.554
14.30 ± 3.00
14.83 ± 3.18
0.643
Midline distance to impacted canine crown tip (mean ± SD) Midline distance to impacted canine apex (mean ± SD)
Left side (n = 68)
p value
Table 5 Comparisons of right and left impacted canine angulations to the midline, lateral incisor, and occlusal plane Variables (degree)
Right side (n = 72)
Left side (n = 68)
p value
Angulation of impacted canine to midline (mean ± SD)
24.26 ± 21.50
21.33 ± 15.74
0.011*
Angulation of impacted canine to lateral incisor (mean ± SD)
34.47 ± 21.95
35.27 ± 18.97
0.230
Angulation of impacted canine to occlusal plane (mean ± SD)
53.38 ± 17.73
55.85 ± 13.88
0.044*
* p \ 0.05, significant difference
maxillary canine impaction was twice as prevalent in women compared with men in their study population [17]. There are two possible explanations for these findings: women may be more vocal than men about situations accompanying impacted canines and/or there may be differences in dentofacial growth and development between women and men [9]. In our study, the breakdown of the maxillary impacted canine locations was as follows: palatal, 54.3%; central, 27.8%; and buccal, 17.8%. Consistent with these findings, Orton et al. [18] reported that 85% of the maxillary impacted canines in their study were found in the palatal region, while the others were found in the line of the arch or a buccal location. Two etiological causes are thought to give rise to palatally located impacted canines, genetic tendencies and lack of guidance (missing or immature lateral incisors). Meanwhile, buccally located impacted canines are often thought to derive from early primary tooth loss and dental arch deficiencies [19]. Sajnani et al. [20] stated that a maxillary impacted canine can be detected after 8 years of age. It is important to achieve radiographic detection of maxillary impacted canine location and angulation at an early age, not only to preclude resorption in the lateral incisors and premolars,
but also to identify pathological tissues. In maxillary impacted canine cases, CBCT is now the imaging method of choice for determining the degree and depth of root resorption in the adjacent teeth [16]. In our study, the maxillary right and left lateral incisors showed similar resorption degrees and common levels of slight resorption. Severe resorption was found in 10 lateral incisors and four first premolars in this study, being similar to the rates of resorption in Walker et al. [21] and Bjerklin et al. [22]. However, Ericson et al. [23] reported a high rate of severe resorption (23%) among lateral incisors, which was much higher than the rate in the present study (6%). The location of a maxillary impacted canine may have an impact on root resorption. Lai et al. [9] found a significant correlation between root resorption and presence of complete alveolar bone impaction of the canine, but also found no correlation between sex and resorption. Untreated or late-diagnosed maxillary impacted canines often cause resorption in lateral incisors, and this is not common in the first premolars. Use of CBCT evaluation can increase the chance of noticing resorption in teeth adjacent to maxillary impacted canines. Furthermore, two-dimensional radiographs were found to be inadequate for imaging of the buccal and palatal resorption regions.
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The present findings revealed significant differences between the right and left maxillary impacted canines in terms of angulation with the midline and occlusal plane. Specifically, the midline angulation of right maxillary impacted canines was significantly higher than that of left maxillary impacted canines, while the occlusal plane angulation of left maxillary impacted canines was significantly higher than that of right maxillary impacted canines. Powers et al. [24] concluded that if an impacted tooth had angulation of [31° to the midline, the chances of the impacted tooth erupting were reduced after deciduous tooth extraction. Alqerban et al. [1] suggest that impacted canine angulation to the lateral incisor is a relevant predictor of canine impaction. Similar to our results, Yu et al. [25] found that the mesial inclination of impacted canines to the occlusal plane ranged from 53.8° to 68.5°. Meanwhile, Ericson et al. [26] reported a relationship between impacted canine angulation and resorption, finding that resorption increased by 50% when the impacted canine angulation to the midline exceeded 25°, and also increased by 50% when the impacted canine inclination to the long axis of the lateral incisor exceeded 28°. Measurements of maxillary impacted canine angulation to adjacent teeth on CBCT images of mixed dentition may help to prevent resorption formation in lateral incisors and premolars. In our study, no significant differences were observed between the right and left sides for the distances of the occlusal plane and maxillary midline to the impacted canine cusp tip and root apex. The mean values for the crown tip of both the right and left impacted canines were nearly 10 mm high relative to the occlusal plane and 9 mm away from the midline. Meanwhile, Yu et al. [25] found that the distances from the impacted canine to the median sagittal plane ranged from 5.4 mm to 8.4 mm. These differences may simply arise from the different study groups used. Specifically, our study included palatally, centrally, and buccally impacted canines, while the study by Yu et al. only included palatally impacted canines. Sajnani et al. [27] found the distance of the canine cusp tip to the occlusal plane was the most important predictor of maxillary canine impaction. Meanwhile, Ericson et al. [11] stated that the more mesially positioned an impacted canine crown was, the less likely passive eruptions were to occur. The use of CBCT allows more precise planning of maxillary impacted canine surgical procedures. According to the literature, use of CBCT evaluations helped to promote the orthodontic treatment process in nearly one-half of all cases examined. The present findings may assist orthodontists in diagnosis and/or prevention, and in planning maxillary impacted canine interventions. Further research is needed to evaluate angular and linear measurements on CBCT images within a larger sample size.
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Conclusions This retrospective study provides three main conclusions. First, the prevalence of maxillary canine impaction was higher among women than among men, and the rate of palatal maxillary canine impaction was nearly three times higher than that of buccal canine impaction. Second, maxillary lateral incisors were more frequently affected than first premolars, and resorption degree 2 (slight) was more frequently seen in both lateral incisors and premolars. Our results also indicated significant differences between right and left maxillary impacted canines, in terms of angulations to the midline and occlusal plane. Third, relative to conventional radiography, three-dimensional CBCT imaging provides more reliable data about the degree of root resorption in adjacent teeth, angulation, and location of impacted canines. Compliance with ethical standards Conflict of interest ˙Ilhan Metin Dag˘suyu, Fatih Kahraman, and Rıdvan Oks¸ ayan declare that they have no conflict of interest. Ethics statement This article does not contain any studies with human or animal subjects performed by any of the authors.
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