- Email: [email protected]
Morphology of maxilla in patients with palatally displaced canines
International Orthodontics 2019; 17: 130–135
Original Article
Websites: www.em-consulte.com www.sciencedirect.com
Morphology of maxilla in patients with palatally displaced canines Amirfarhang Miresmaeili 1, Abbas Shokri 2, Fatemeh Salemi 2, Fatemeh Dehghani 1, Vahid Shahidi-Zandi 3, Ramin Rad 4, Maryam Shahdoost 5
Available online: 14 February 2019
1. Department of Orthodontics, Dental school, Hamadan University of Medical Sciences, Hamadan, Iran 2. Department of Oral and Maxillofacial Radiology, Hamadan University of Medical Sciences, Hamadan, Iran 3. Department of Orthodontics, Faculty of Dentistry, Lorestan University of Medical Sciences, Khorramabad, Iran 4. Private practice, Hamadan, Iran 5. Department of Biostatistics and Epidemiology, Research Center for Health Sciences, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
Correspondence: Vahid Shahidi-Zandi, Shahid Fahmideh Street, Hamadan, Iran. [email protected]
130
Keywords Maxilla Impacted tooth Cone-beam CT
Summary Objectives > The aim of this study was to investigate the possible relationship between the morphology of maxilla and the palatally displaced canines (PDC). Materials and methods > In this cross-sectional study, there were 101 patients (45 males, 56 females) aged 12 to 16 years, referred to Hamadan school of dentistry in 2014. They were divided into 3 groups: the bilateral PDC (PDCb) group (male = 15, female = 21), the unilateral PDC (PDCu) group (male = 16, female = 19), and the control group (male = 14, female = 16). Five morphology related variables including intermolar width, maxillary arch length, palatal vault depth, palatal intermolar area, and nasal width were measured using CBCT images with Dolphin Imaging software, version 11.5. Statistical analysis was performed with ANOVA and the Dunnett test using SPSS software, version 16.0. Results > Only the palatal intermolar area and the palatal vault depth values were significantly less in the PDCu and the PDCb groups than those in the control group (the palatal intermolar area: 376.17, 381.93, and 423.75 mm2, the palatal vault depth: 13.19, 13.42, and 14.59 mm; respectively; P < 0.05). For all the variables, there was no statistically significant difference between the PDCu and PDCb groups. Conclusion > Decreased palatal vault depth and palatal intermolar area may be correlated with greater chance of palatal displacement of canines. Future prospective studies in mixed dentition patients are needed as a predictive factor to find the probability of PDC.
tome 17 > n81 > March 2019 https://doi.org/10.1016/j.ortho.2019.01.012 © 2019 CEO. Published by Elsevier Masson SAS. All rights reserved.
Résumé Anatomie du maxillaire des patients souffrant de canines palatines ectopiques Objectifs > Le but de cette étude était d'étudier la possibilité d'une relation entre la morphologie du maxillaire et l'ectopie palatine des canines (PDC : palatal displaced canine). Matériels et méthodes > Dans cette étude transversale, 101 patients (45 garçons et 56 filles) âgés de 12 à 16 ans ont été orientés vers l'école dentaire d'Hamadan en 2014–2015 et ont été répartis en 3 groupes : le groupe bilatéral PDC (PDCb) (garçons = 15, filles = 21), le groupe unilatéral PDC (PDCu) (garçons = 16, filles = 19) et le groupe témoin (garçons = 14, filles = 16). Cinq variables liées à la morphologie, dont la largeur inter-molaire, la longueur de l'arcade maxillaire, la profondeur de la voûte palatine, la zone palatine inter-molaire et la largeur nasale, ont été mesurées sur les images CBCT avec la version 11.5 du logiciel d'imagerie Dolphin. L'analyse statistique a été réalisée avec une ANOVA et un test de Dunnett sur le logiciel SPSS, version 16.0. Résultats > Seules les valeurs de la zone palatine inter-molaire et de la profondeur de la voûte palatine étaient significativement plus faibles dans les groupes PDCu et PDCb que dans le groupe témoin (la zone palatine inter-molaire) : 376,17, 381,93 et 423,75 mm2. La profondeur de la voûte palatine : 13,19, 13,42 et 14,59 mm respectivement ; p < 0,05. Aucune différence statistiquement significative n'a été constatée entre les groupes PDCu et PDCb sur l'ensemble des variables. Conclusion > Une diminution de la profondeur de la voûte palatine et de la zone palatine intermolaire peut être corrélée à une plus grande probabilité d'ectopie canine palatine. D'autres études prospectives chez des patients en dentition mixte sont nécessaires pour évaluer le facteur prédictif et la probabilité de la PDC.
Introduction Maxillary canines are the second teeth most susceptible to impact after third molars [1,2]. The prevalence of canine impaction is in the range of 1% to 5% in various studies looked at [3–6] and is measured as 2.8% in a group from, 'A selected Iranian population' [7]. The PDC is 2 to 3 times more frequent in girls than boys [8–11], and palatal impaction is 3 to 6 times more frequent than buckle impaction in Caucasians [12–14]. Although unilateral ectopic eruptions are more frequent, bilateral maxillary canine impaction is not unusual [15]. According to Sacerdoti and Baccetti [16], both PDCb and PDCu are significantly associated with small-sized upper lateral incisors, and PDCb exhibited a significant association to aplasia of upper lateral incisors, whereas PDCu was significantly associated with aplasia of third molars. They also suggested that the high prevalence of PDCb confirms the genetic component of its aetiology. In a retrospective study, McConnell et al. [17] found an association between maxillary canine impaction and maxillary transverse deficiency. The difference between the maxillary canine impaction and the normal group was attributed to intercanine arch width, and no difference was detected in intermolar arch width between the two groups. However, Langberg and Peck [18] suggested that the method of McConnell et al. for measuring intercanine arch width was unreliable and subjective, because they attempted to predetermine visually where the unerupted canine should normally erupt, in order to establish
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the measurement points. In their investigation, they found no statistically significant difference between the impacted and control groups in either anterior or posterior dental arch widths. In agreement with this study, Saiar et al. [19] found no association between PDC and maxillary skeletal width. Finally, Hong et al. [20] and Yan et al. [21] suggested that there was no correlation between maxillary transverse dimensions and PDC. McConnell et al. [17] and Langberg and Peck [18] used dental casts to measure maxillary skeletal width, whereas Saiar et al. [19] assessed maxillary skeletal width deficiencies by using posteroanterior cephalograms. In our recent study, however, we used CBCT images instead of casts or two-dimensional radiographs. More recently, Yan et al. [21] used CBCT images to measure maxillary skeletal width (from points J to J), and, Hong et al. [20] measured basal bone widths and intermolar dental widths using the same method. Using the CBCT for measuring palatal intermolar area, as well as distance, and localizing the impacted canine was the aim of the present study. This study was designed to investigate and compare the morphology of maxilla in the PDCu, PDCb, and in normal patients.
Material and methods The sample size was calculated according to Langberg and Peck [18] using the following equation with alpha error and the
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Mots clés Maxillaire Dent incluse Cone-beam CT
Original Article
Morphology of maxilla in patients with palatally displaced canines
Original Article
A. Miresmaeili, A. Shokri, F. Salemi, F. Dehghani, V. Shahidi-Zandi, R. Rad, et al.
statistical power of 5% and 80%, respectively.
n¼
2Sp2 Z 11=2 þ Z 1b d
2
2
In this cross-sectional study, after receiving Institutional Review Board Approval from Hamadan University with Res. Proj. 16/35/1/5768/P, 101 patients referred to the orthodontics division at the dental school of Hamadan University of medical sciences in 2014–15 were enrolled. Among them, 36 patients (m = 15, f = 21) were placed in the PDCb group, 35 patients (m = 16, f = 19) in the PDCu group, and 30 patients (m = 14, f = 16) in the control group (table I). All patients were aged between 12 and 16, had not received any orthodontic treatment, and had CBCT images. The control group was comprised of patients with normal eruption of canines and normal occlusion. The CBCT images were taken because of trauma or diagnostic issues such as evaluation of the miniscrew site. The PDCb group consisted of patients with the impacted canine on one side, and the PDCu group consisted of patients with the impacted canine on both sides. Impaction signifies a considerable delay in canine eruption with no future chance for eruption due to clinical and radiographic evaluations [22,23]. Exclusion criteria were as follows: patients with cleft lip and palate, patients with supernumerary teeth, patients with multiple impacted teeth, patients with congenital missing teeth, and patients with a systemic disease. The patients in the control and case groups were matched by gender and age. The CBCT images were acquired using a NewTom 3G machine (QR-DVT 9000, Versona, Italy) with the field of view (FOV) of 6, 9, and 12. The information obtained from the images was converted to Dicom format, transmitted to Dolphin 3-D imaging software version 11.5 (Chatsworth, Calif), and evaluated using 3-D views. Firstly, the CBCT images were oriented in such a way that the sagittal plane coincided with the maxillary skeletal midline, and, the occlusal plane was positioned parallel to the true horizontal line.
In the axial view, to measure the intermolar width, the image was clipped so that the mesiopalatal cusp tips of the first molars could be clearly seen. Then, the length of the line connecting the mesiopalatal cusp tip of one side to the opposite side was measured (figure 1a–b). To measure the arch length, a section was chosen from apical to coronal areas whereby the first molar and the second premolar had the most contact, and a line connected the middle of this contact to the same point on the opposite side. The distance from the intersection of this line with the midsagittal plane to the contact of central incisors was measured (figure 1a–b). In the coronal view, to measure the palatal vault depth, a section was chosen with the least distance to the palatal cusps of both sides, and a line connected CEJ of the 1st molar on one side to the similar point on the opposite side. The distance from the middle of the mentioned line to the line perpendicular from the palate to this line was measured (figure 2a). To measure the nasal width, a line connected the widest segment of the lower third of the nasal cavity on one side to the opposite side in the former section, and the length of this line was measured (figure 2b). The last variable measured for this view and section, was the palatal intermolar area and was achieved by computing the surrounding region with seven points including the CEJ of right and left 1st molars, the corner of the palate on both sides, the middle of right and left palatal halves, and the middle point of the palate (figure 2c). Eventually, the presence or absence of resorption of the adjacent teeth with any concavity more than 1 mm was evaluated at the multiplanar views along the root of adjacent teeth. To measure intraexaminer agreement, 20% of the sample size (20 patients) were randomly selected and revaluated 2 weeks later. Descriptive analysis including means, standard deviations, and ranges were calculated for all measurements. The one-way analysis of variance was used to determine significant differences between groups using SPSS for Windows software, version 16.0 (SPSS Inc., Chicago, IL, USA). The Dunnett post-hoc test was utilized if the ANOVA test revealed any statistically
TABLE I Demographic characteristics of the sample. Group
Number
Gender
Mean age
Male (%)
Female (%)
FOV 6-inch
9-inch
12-inch
PDCu
36
21 (58.3)
15 (41.7)
13.9
14
10
12
PDCb
35
19 (54.3)
16 (45.7)
14.2
13
12
10
Controls
30
16 (53.3)
14 (46.7)
14.6
9
11
10
Total
101
56 (55.4)
45 (44.6)
14.2
36
33
32
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FOV: field of view; PDCu: unilateral palatally displaced canines; PDCb: bilateral palatally displaced canines.
tome 17 > n81 > March 2019
Original Article
Morphology of maxilla in patients with palatally displaced canines
Figure 1 a–b: axial view; a: intermolar width measurement; b: arch length measurement
Figure 2 a–c: coronal view; a: palatal vault depth measurement; b: nasal width measurement; c: palatal intermolar area measurement
Results The interclass correlation coefficient (ICC) was r = 0.98 for all the measured variables, except for nasal width (r = 0.86), indicating excellent intraobserver reliability. The average values and standard deviations for each item in the 3 groups are given in table I. Both the palatal vault depth and the intermolar palatal area showed statistically significant differences using one-way ANOVA (P < 0.05). The Dunnett post-hoc test shows statistically significant differences for both variables in the PDCu and the PDCb groups compared to those in the control group (the palatal intermolar area: 376.17, 381.93, and 423.75 mm2, the palatal vault depth: 13.19, 13.42, and 14.59 mm, respectively); however, no significant difference existed between the PDCu and the PDCb group (table II). The lateral incisor root resorption was more commonly found in the PDCu group (5 subjects, or 14%) than the PDCb group (2 subjects, or 6%); however, this difference was not statistically
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significant (P = 0.081). In total, 7 out of 71 patients in the palatally displaced canine groups had lateral incisor root resorption (10%).
Discussion The present study investigates the morphology of maxilla in PDC patients and its relationship with that of a control group of age and gender-matched orthodontic patients. The results revealed that there is no statistically significant difference between the PDC groups and the control group among the evaluated variables, except for the palatal vault depth and the palatal intermolar area, indicating that both variables decrease in the PDC. A point of great importance to note is that in most of the investigated studies, except for Hong et al. [20] and Yan et al. [21], the panoramic radiographs or posteroanterior cephalograms were used to diagnose the PDC. These radiographic techniques have a higher incidence of error, especially when compared to CBCT due to their distortion, magnification, and overlap of anatomical structures.
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significant difference. The level of significance for all statistical tests was set at P < 0.05.
Original Article
A. Miresmaeili, A. Shokri, F. Salemi, F. Dehghani, V. Shahidi-Zandi, R. Rad, et al.
TABLE II Mean, standard deviations, and comparison of variables in the groups with ANOVA and Dunnett test. Variable
Group
ANOVA test P-value
Dunnett test P-value
PDCu
PDCb
C
PDCu/C
PDCb/C
PDCu/PDCb
IMW (mm)
36.90 3.08
37.43 2.90
38.10 2.13
0.242
NA
NA
0.505
AL (mm)
24.11 2.70
24.63 2.41
25.23 1.87
0.175
NA
1
PVD (mm)
13.19 2.50
13.42 2.37
14.59 1.77
0.003
NW (mm)
30.79 3.87
31.00 2.99
31.15 2.10
0.861
2
IPA (mm )
376.17 69.17
381.93 71.36
423.75 55.50
0.026
NA 1
NA 1
< 0.0001
0.008
0.001
0.384 1
0.336
NA 1
< 0.0001
0.924 1
0.149
NA: not assessed; PDCu: unilateral palatally displaced canines; PDCb: bilateral palatally displaced canines; C: controls; IMW: intermolar width; AL: arch length; PVD: palatal vault depth; NW: nasal width; IPA: intermolar palatal area. 1 Statistically significant (P < 0.05).
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Deep palatal vault indicates maxillary vertical excess that is highly influential in the positioning of the permanent teeth buds. Kim et al. [24] concluded that the palatal vault depth is significantly less in the buccally impacted canine group than in the palatally impacted canine group, but no comparison was made with a control group. We found no previous, similar study measuring the palatal intermolar area; therefore, we could not compare our study with others. Regarding the decrease in the palatal intermolar area and no change in the intermolar width, it can be concluded that the palate is shallower in the PDC, which is confirmed with less palatal vault depth. This may be a contributory factor for impaction. The study's results indicate that there is no statistically significant difference, dentally, in the intermolar width between the PDC groups, and the control group. Similar results were reported by Yan et al. [21], Saiar et al. [19], and Langberg and Peck [18]. In contrast, Al-nimri and Gharaibeh [25] stated that PDC occurred more frequently in those with larger intermolar widths. On the other hand, McConnell et al. [17] found an obvious transverse maxillary deficiency in the intermolar width in the PDC patients. Similar to Langberg and Peck [18], we found no relationship between maxillary arch length and PDC. Meanwhile, our study contradicts the results of McConnell et al. [17] As Langberg and Peck stated: "We can confidently conclude that maxillary arch width is not a primary contributory factor in the genesis of the PDC anomaly'' [18]. The clinical evidence indicates that the size and form of maxilla show no difference between the normal and PDC subjects [11]. If transverse maxillary deficiency were a major etiologic factor of the PDC, it would be expected that the Asian populations with more frequency of maxillary underdevelopment than the Europeans, would exhibit more prevalence of the PDC anomaly, which is not true in this case [26–28]. It is worth mentioning that two studies by Kim et al. [24] and Fattahi et al. [29] compared the intermolar width and the
maxillary arch length in the PDC with a buccally impacted canine group. The former concluded that the PDC patients had a longer and narrower maxillary arch, while the latter found no clinically significant difference between the two groups. Nevertheless, these findings cannot be compared to our study, since a control group was not investigated. In agreement with our study, Saiar et al. [19] found no relationship between the nasal width and the PDC, and it was rejected that nasal width is slightly greater in normal subjects than in the PDC patients. In addition, in a brand new comparison, the present study revealed that there is no difference between the PDCu and the PDCb groups with regard to the morphology of maxilla. No studies have been carried out with respect to this comparison. Resorption of the lateral incisor root, as the secondary outcome, is less in our study compared to that of Liu et al. [30], and Ericson and Kurol [31] (10%, 27.2%, and 48%, respectively). Prospective studies on this issue, especially on mixed dentition subjects from the age 10 years, and recruiting a buccally impacted canine group, are recommended. It is clear that utilization of the CBCT technique for diagnosis and measurement is mandatory.
Conclusions According to the present study, decreased palatal vault depth and palatal intermolar area may contribute to and increase the chances of palatal displacement of canines. Therefore, we can cautionarily conclude that these might be contributory factors to impaction. Disclosure of interest: the authors declare that they have no competing interest.
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[22] Mason C, Papadakou P, Roberts GJ. The radiographic localization of impacted maxillary canines: a comparison of methods. Eur J Orthod 2001;23(1):25–34. [23] Richardson G, Russell KA. A review of impacted permanent maxillary cuspids-diagnosis and prevention. J Can Dent Assoc 2000;66(9):497–502. [24] Kim Y, Hyun H-K, Jang K-T. Interrelationship between the position of impacted maxillary canines and the morphology of the maxilla. Am J Orthod Dentofacial Orthop 2012;141 (5):556–62. [25] Al-Nimri K, Gharaibeh T. Space conditions and dental and occlusal features in patients with palatally impacted maxillary canines: an aetiological study. Eur J Orthod 2005;27 (5):461–5. [26] Suhr C. [Orthodontic considerations in maxillary impacted canines]. Taehan Ch'ikkwa Uisa Hyophoe chi 1987;25(1):59–70. [27] Takeshita K, Shimoyama K, Matsuura A, Ohtsuka E, Taki H. 4 cases of class 3 malocclusion with impacted maxillary canine. Nihon Kyo¯sei Shika Gakkai zasshi 1972;31 (1):247. [28] Ito M, Nozaka K, Moriguchi O, et al. [The clinical observation of exposure and traction cases of impacted teeth]. Shoni shikagaku zasshi 1986;24(4):643–52. [29] Fattahi H, Ghaeed F, Alipour A. Association between maxillary canine impaction and arch dimensions. Aust Orthod J 2012;28(1):57. [30] Liu DG, Zhang WL, Zhang ZY, Wu YT, Ma XC. Localization of impacted maxillary canines and observation of adjacent incisor resorption with cone-beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105(1):91–8. [31] Ericson S, Kurol J. Resorption of incisors after ectopic eruption of maxillary canines: a CT study. Angle Orthod 2000;70(6):415–23.
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References
Original Article
Morphology of maxilla in patients with palatally displaced canines
Original Article
Websites: www.em-consulte.com www.sciencedirect.com
Morphology of maxilla in patients with palatally displaced canines Amirfarhang Miresmaeili 1, Abbas Shokri 2, Fatemeh Salemi 2, Fatemeh Dehghani 1, Vahid Shahidi-Zandi 3, Ramin Rad 4, Maryam Shahdoost 5
Available online: 14 February 2019
1. Department of Orthodontics, Dental school, Hamadan University of Medical Sciences, Hamadan, Iran 2. Department of Oral and Maxillofacial Radiology, Hamadan University of Medical Sciences, Hamadan, Iran 3. Department of Orthodontics, Faculty of Dentistry, Lorestan University of Medical Sciences, Khorramabad, Iran 4. Private practice, Hamadan, Iran 5. Department of Biostatistics and Epidemiology, Research Center for Health Sciences, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
Correspondence: Vahid Shahidi-Zandi, Shahid Fahmideh Street, Hamadan, Iran. [email protected]
130
Keywords Maxilla Impacted tooth Cone-beam CT
Summary Objectives > The aim of this study was to investigate the possible relationship between the morphology of maxilla and the palatally displaced canines (PDC). Materials and methods > In this cross-sectional study, there were 101 patients (45 males, 56 females) aged 12 to 16 years, referred to Hamadan school of dentistry in 2014. They were divided into 3 groups: the bilateral PDC (PDCb) group (male = 15, female = 21), the unilateral PDC (PDCu) group (male = 16, female = 19), and the control group (male = 14, female = 16). Five morphology related variables including intermolar width, maxillary arch length, palatal vault depth, palatal intermolar area, and nasal width were measured using CBCT images with Dolphin Imaging software, version 11.5. Statistical analysis was performed with ANOVA and the Dunnett test using SPSS software, version 16.0. Results > Only the palatal intermolar area and the palatal vault depth values were significantly less in the PDCu and the PDCb groups than those in the control group (the palatal intermolar area: 376.17, 381.93, and 423.75 mm2, the palatal vault depth: 13.19, 13.42, and 14.59 mm; respectively; P < 0.05). For all the variables, there was no statistically significant difference between the PDCu and PDCb groups. Conclusion > Decreased palatal vault depth and palatal intermolar area may be correlated with greater chance of palatal displacement of canines. Future prospective studies in mixed dentition patients are needed as a predictive factor to find the probability of PDC.
tome 17 > n81 > March 2019 https://doi.org/10.1016/j.ortho.2019.01.012 © 2019 CEO. Published by Elsevier Masson SAS. All rights reserved.
Résumé Anatomie du maxillaire des patients souffrant de canines palatines ectopiques Objectifs > Le but de cette étude était d'étudier la possibilité d'une relation entre la morphologie du maxillaire et l'ectopie palatine des canines (PDC : palatal displaced canine). Matériels et méthodes > Dans cette étude transversale, 101 patients (45 garçons et 56 filles) âgés de 12 à 16 ans ont été orientés vers l'école dentaire d'Hamadan en 2014–2015 et ont été répartis en 3 groupes : le groupe bilatéral PDC (PDCb) (garçons = 15, filles = 21), le groupe unilatéral PDC (PDCu) (garçons = 16, filles = 19) et le groupe témoin (garçons = 14, filles = 16). Cinq variables liées à la morphologie, dont la largeur inter-molaire, la longueur de l'arcade maxillaire, la profondeur de la voûte palatine, la zone palatine inter-molaire et la largeur nasale, ont été mesurées sur les images CBCT avec la version 11.5 du logiciel d'imagerie Dolphin. L'analyse statistique a été réalisée avec une ANOVA et un test de Dunnett sur le logiciel SPSS, version 16.0. Résultats > Seules les valeurs de la zone palatine inter-molaire et de la profondeur de la voûte palatine étaient significativement plus faibles dans les groupes PDCu et PDCb que dans le groupe témoin (la zone palatine inter-molaire) : 376,17, 381,93 et 423,75 mm2. La profondeur de la voûte palatine : 13,19, 13,42 et 14,59 mm respectivement ; p < 0,05. Aucune différence statistiquement significative n'a été constatée entre les groupes PDCu et PDCb sur l'ensemble des variables. Conclusion > Une diminution de la profondeur de la voûte palatine et de la zone palatine intermolaire peut être corrélée à une plus grande probabilité d'ectopie canine palatine. D'autres études prospectives chez des patients en dentition mixte sont nécessaires pour évaluer le facteur prédictif et la probabilité de la PDC.
Introduction Maxillary canines are the second teeth most susceptible to impact after third molars [1,2]. The prevalence of canine impaction is in the range of 1% to 5% in various studies looked at [3–6] and is measured as 2.8% in a group from, 'A selected Iranian population' [7]. The PDC is 2 to 3 times more frequent in girls than boys [8–11], and palatal impaction is 3 to 6 times more frequent than buckle impaction in Caucasians [12–14]. Although unilateral ectopic eruptions are more frequent, bilateral maxillary canine impaction is not unusual [15]. According to Sacerdoti and Baccetti [16], both PDCb and PDCu are significantly associated with small-sized upper lateral incisors, and PDCb exhibited a significant association to aplasia of upper lateral incisors, whereas PDCu was significantly associated with aplasia of third molars. They also suggested that the high prevalence of PDCb confirms the genetic component of its aetiology. In a retrospective study, McConnell et al. [17] found an association between maxillary canine impaction and maxillary transverse deficiency. The difference between the maxillary canine impaction and the normal group was attributed to intercanine arch width, and no difference was detected in intermolar arch width between the two groups. However, Langberg and Peck [18] suggested that the method of McConnell et al. for measuring intercanine arch width was unreliable and subjective, because they attempted to predetermine visually where the unerupted canine should normally erupt, in order to establish
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the measurement points. In their investigation, they found no statistically significant difference between the impacted and control groups in either anterior or posterior dental arch widths. In agreement with this study, Saiar et al. [19] found no association between PDC and maxillary skeletal width. Finally, Hong et al. [20] and Yan et al. [21] suggested that there was no correlation between maxillary transverse dimensions and PDC. McConnell et al. [17] and Langberg and Peck [18] used dental casts to measure maxillary skeletal width, whereas Saiar et al. [19] assessed maxillary skeletal width deficiencies by using posteroanterior cephalograms. In our recent study, however, we used CBCT images instead of casts or two-dimensional radiographs. More recently, Yan et al. [21] used CBCT images to measure maxillary skeletal width (from points J to J), and, Hong et al. [20] measured basal bone widths and intermolar dental widths using the same method. Using the CBCT for measuring palatal intermolar area, as well as distance, and localizing the impacted canine was the aim of the present study. This study was designed to investigate and compare the morphology of maxilla in the PDCu, PDCb, and in normal patients.
Material and methods The sample size was calculated according to Langberg and Peck [18] using the following equation with alpha error and the
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Mots clés Maxillaire Dent incluse Cone-beam CT
Original Article
Morphology of maxilla in patients with palatally displaced canines
Original Article
A. Miresmaeili, A. Shokri, F. Salemi, F. Dehghani, V. Shahidi-Zandi, R. Rad, et al.
statistical power of 5% and 80%, respectively.
n¼
2Sp2 Z 11=2 þ Z 1b d
2
2
In this cross-sectional study, after receiving Institutional Review Board Approval from Hamadan University with Res. Proj. 16/35/1/5768/P, 101 patients referred to the orthodontics division at the dental school of Hamadan University of medical sciences in 2014–15 were enrolled. Among them, 36 patients (m = 15, f = 21) were placed in the PDCb group, 35 patients (m = 16, f = 19) in the PDCu group, and 30 patients (m = 14, f = 16) in the control group (table I). All patients were aged between 12 and 16, had not received any orthodontic treatment, and had CBCT images. The control group was comprised of patients with normal eruption of canines and normal occlusion. The CBCT images were taken because of trauma or diagnostic issues such as evaluation of the miniscrew site. The PDCb group consisted of patients with the impacted canine on one side, and the PDCu group consisted of patients with the impacted canine on both sides. Impaction signifies a considerable delay in canine eruption with no future chance for eruption due to clinical and radiographic evaluations [22,23]. Exclusion criteria were as follows: patients with cleft lip and palate, patients with supernumerary teeth, patients with multiple impacted teeth, patients with congenital missing teeth, and patients with a systemic disease. The patients in the control and case groups were matched by gender and age. The CBCT images were acquired using a NewTom 3G machine (QR-DVT 9000, Versona, Italy) with the field of view (FOV) of 6, 9, and 12. The information obtained from the images was converted to Dicom format, transmitted to Dolphin 3-D imaging software version 11.5 (Chatsworth, Calif), and evaluated using 3-D views. Firstly, the CBCT images were oriented in such a way that the sagittal plane coincided with the maxillary skeletal midline, and, the occlusal plane was positioned parallel to the true horizontal line.
In the axial view, to measure the intermolar width, the image was clipped so that the mesiopalatal cusp tips of the first molars could be clearly seen. Then, the length of the line connecting the mesiopalatal cusp tip of one side to the opposite side was measured (figure 1a–b). To measure the arch length, a section was chosen from apical to coronal areas whereby the first molar and the second premolar had the most contact, and a line connected the middle of this contact to the same point on the opposite side. The distance from the intersection of this line with the midsagittal plane to the contact of central incisors was measured (figure 1a–b). In the coronal view, to measure the palatal vault depth, a section was chosen with the least distance to the palatal cusps of both sides, and a line connected CEJ of the 1st molar on one side to the similar point on the opposite side. The distance from the middle of the mentioned line to the line perpendicular from the palate to this line was measured (figure 2a). To measure the nasal width, a line connected the widest segment of the lower third of the nasal cavity on one side to the opposite side in the former section, and the length of this line was measured (figure 2b). The last variable measured for this view and section, was the palatal intermolar area and was achieved by computing the surrounding region with seven points including the CEJ of right and left 1st molars, the corner of the palate on both sides, the middle of right and left palatal halves, and the middle point of the palate (figure 2c). Eventually, the presence or absence of resorption of the adjacent teeth with any concavity more than 1 mm was evaluated at the multiplanar views along the root of adjacent teeth. To measure intraexaminer agreement, 20% of the sample size (20 patients) were randomly selected and revaluated 2 weeks later. Descriptive analysis including means, standard deviations, and ranges were calculated for all measurements. The one-way analysis of variance was used to determine significant differences between groups using SPSS for Windows software, version 16.0 (SPSS Inc., Chicago, IL, USA). The Dunnett post-hoc test was utilized if the ANOVA test revealed any statistically
TABLE I Demographic characteristics of the sample. Group
Number
Gender
Mean age
Male (%)
Female (%)
FOV 6-inch
9-inch
12-inch
PDCu
36
21 (58.3)
15 (41.7)
13.9
14
10
12
PDCb
35
19 (54.3)
16 (45.7)
14.2
13
12
10
Controls
30
16 (53.3)
14 (46.7)
14.6
9
11
10
Total
101
56 (55.4)
45 (44.6)
14.2
36
33
32
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FOV: field of view; PDCu: unilateral palatally displaced canines; PDCb: bilateral palatally displaced canines.
tome 17 > n81 > March 2019
Original Article
Morphology of maxilla in patients with palatally displaced canines
Figure 1 a–b: axial view; a: intermolar width measurement; b: arch length measurement
Figure 2 a–c: coronal view; a: palatal vault depth measurement; b: nasal width measurement; c: palatal intermolar area measurement
Results The interclass correlation coefficient (ICC) was r = 0.98 for all the measured variables, except for nasal width (r = 0.86), indicating excellent intraobserver reliability. The average values and standard deviations for each item in the 3 groups are given in table I. Both the palatal vault depth and the intermolar palatal area showed statistically significant differences using one-way ANOVA (P < 0.05). The Dunnett post-hoc test shows statistically significant differences for both variables in the PDCu and the PDCb groups compared to those in the control group (the palatal intermolar area: 376.17, 381.93, and 423.75 mm2, the palatal vault depth: 13.19, 13.42, and 14.59 mm, respectively); however, no significant difference existed between the PDCu and the PDCb group (table II). The lateral incisor root resorption was more commonly found in the PDCu group (5 subjects, or 14%) than the PDCb group (2 subjects, or 6%); however, this difference was not statistically
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significant (P = 0.081). In total, 7 out of 71 patients in the palatally displaced canine groups had lateral incisor root resorption (10%).
Discussion The present study investigates the morphology of maxilla in PDC patients and its relationship with that of a control group of age and gender-matched orthodontic patients. The results revealed that there is no statistically significant difference between the PDC groups and the control group among the evaluated variables, except for the palatal vault depth and the palatal intermolar area, indicating that both variables decrease in the PDC. A point of great importance to note is that in most of the investigated studies, except for Hong et al. [20] and Yan et al. [21], the panoramic radiographs or posteroanterior cephalograms were used to diagnose the PDC. These radiographic techniques have a higher incidence of error, especially when compared to CBCT due to their distortion, magnification, and overlap of anatomical structures.
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significant difference. The level of significance for all statistical tests was set at P < 0.05.
Original Article
A. Miresmaeili, A. Shokri, F. Salemi, F. Dehghani, V. Shahidi-Zandi, R. Rad, et al.
TABLE II Mean, standard deviations, and comparison of variables in the groups with ANOVA and Dunnett test. Variable
Group
ANOVA test P-value
Dunnett test P-value
PDCu
PDCb
C
PDCu/C
PDCb/C
PDCu/PDCb
IMW (mm)
36.90 3.08
37.43 2.90
38.10 2.13
0.242
NA
NA
0.505
AL (mm)
24.11 2.70
24.63 2.41
25.23 1.87
0.175
NA
1
PVD (mm)
13.19 2.50
13.42 2.37
14.59 1.77
0.003
NW (mm)
30.79 3.87
31.00 2.99
31.15 2.10
0.861
2
IPA (mm )
376.17 69.17
381.93 71.36
423.75 55.50
0.026
NA 1
NA 1
< 0.0001
0.008
0.001
0.384 1
0.336
NA 1
< 0.0001
0.924 1
0.149
NA: not assessed; PDCu: unilateral palatally displaced canines; PDCb: bilateral palatally displaced canines; C: controls; IMW: intermolar width; AL: arch length; PVD: palatal vault depth; NW: nasal width; IPA: intermolar palatal area. 1 Statistically significant (P < 0.05).
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Deep palatal vault indicates maxillary vertical excess that is highly influential in the positioning of the permanent teeth buds. Kim et al. [24] concluded that the palatal vault depth is significantly less in the buccally impacted canine group than in the palatally impacted canine group, but no comparison was made with a control group. We found no previous, similar study measuring the palatal intermolar area; therefore, we could not compare our study with others. Regarding the decrease in the palatal intermolar area and no change in the intermolar width, it can be concluded that the palate is shallower in the PDC, which is confirmed with less palatal vault depth. This may be a contributory factor for impaction. The study's results indicate that there is no statistically significant difference, dentally, in the intermolar width between the PDC groups, and the control group. Similar results were reported by Yan et al. [21], Saiar et al. [19], and Langberg and Peck [18]. In contrast, Al-nimri and Gharaibeh [25] stated that PDC occurred more frequently in those with larger intermolar widths. On the other hand, McConnell et al. [17] found an obvious transverse maxillary deficiency in the intermolar width in the PDC patients. Similar to Langberg and Peck [18], we found no relationship between maxillary arch length and PDC. Meanwhile, our study contradicts the results of McConnell et al. [17] As Langberg and Peck stated: "We can confidently conclude that maxillary arch width is not a primary contributory factor in the genesis of the PDC anomaly'' [18]. The clinical evidence indicates that the size and form of maxilla show no difference between the normal and PDC subjects [11]. If transverse maxillary deficiency were a major etiologic factor of the PDC, it would be expected that the Asian populations with more frequency of maxillary underdevelopment than the Europeans, would exhibit more prevalence of the PDC anomaly, which is not true in this case [26–28]. It is worth mentioning that two studies by Kim et al. [24] and Fattahi et al. [29] compared the intermolar width and the
maxillary arch length in the PDC with a buccally impacted canine group. The former concluded that the PDC patients had a longer and narrower maxillary arch, while the latter found no clinically significant difference between the two groups. Nevertheless, these findings cannot be compared to our study, since a control group was not investigated. In agreement with our study, Saiar et al. [19] found no relationship between the nasal width and the PDC, and it was rejected that nasal width is slightly greater in normal subjects than in the PDC patients. In addition, in a brand new comparison, the present study revealed that there is no difference between the PDCu and the PDCb groups with regard to the morphology of maxilla. No studies have been carried out with respect to this comparison. Resorption of the lateral incisor root, as the secondary outcome, is less in our study compared to that of Liu et al. [30], and Ericson and Kurol [31] (10%, 27.2%, and 48%, respectively). Prospective studies on this issue, especially on mixed dentition subjects from the age 10 years, and recruiting a buccally impacted canine group, are recommended. It is clear that utilization of the CBCT technique for diagnosis and measurement is mandatory.
Conclusions According to the present study, decreased palatal vault depth and palatal intermolar area may contribute to and increase the chances of palatal displacement of canines. Therefore, we can cautionarily conclude that these might be contributory factors to impaction. Disclosure of interest: the authors declare that they have no competing interest.
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References
Original Article
Morphology of maxilla in patients with palatally displaced canines