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Year : 2021  |  Volume : 13  |  Issue : 1  |  Page : 34-39

The bridge connecting sella turcica and palatally impacted canine

Department of Orthodontics and Dentofacial Orthopedics, Bhojia Dental College, Baddi, Himachal Pradesh, India

Date of Submission27-Feb-2020
Date of Decision21-Aug-2020
Date of Acceptance22-Sep-2020
Date of Web Publication31-Dec-2020

Correspondence Address:
Ashwin Pradhan
Purano Namchi, Namchi, South Sikkim, Sikkim
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJDS.IJDS_30_20

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Introduction: The calcification of sella trucica bridge might be positively associated with canine impaction, the reason being that sella turcica, dental epithelial progenitor cells along with maxilla, palatal, and frontonasal development share a common embryological origin (neural crest cells). Therefore their assessment might provide useful clinical information in predicting palatal canine impaction. Aim: To evaluate the calcification of sella turcica bridging in patients with palatally impacted canine. Materials and method: A total of 21 pretreatment lateral cephalograms of patients with palatally impacted canine and 29 patients with normally erupted canine were selected for the study. Lateral cephalograms of the patients were acquired and landmark were identified and marked. Various Sella values (sella length/interclinoid distance, sella depth, sella diameter) were measured. The values obtained were then subjected to statistical analysis. Result: Suggested that patients with a palatally impacted canine showed smaller interclinoid distance. The frequency of sella bridging was significantly higher in subjects with canine impaction than in controls (P <0.001). Conclusion: Sella bridging is frequently found in palatally impacted canines. The smaller intercliniod distance could be an indicative factor for diagnosis of palatal canine impaction.

Keywords: Palatal canine impaction, sella calcification, sella turcica, sella turcica bridging

How to cite this article:
Aggarwal I, Pradhan A, Mittal S, Bhullar MK, Sachdeva A, Setia M. The bridge connecting sella turcica and palatally impacted canine. Indian J Dent Sci 2021;13:34-9

How to cite this URL:
Aggarwal I, Pradhan A, Mittal S, Bhullar MK, Sachdeva A, Setia M. The bridge connecting sella turcica and palatally impacted canine. Indian J Dent Sci [serial online] 2021 [cited 2021 Jan 16];13:34-9. Available from: http://www.ijds.in/text.asp?2021/13/1/34/305973

  Introduction Top

Any morphological defect or anomaly affecting the maxillary canine has a negative impact on the smile and facial esthetics.[1] The impaction of tooth has been studied by many authors, and various terminologies have been given in the literature to define impaction including delayed eruption, primary retention, submerged teeth, and impacted teeth.[2]

The incidence of maxillary canine impaction is found to be 1.1%–13% of the population with a higher prevalence in females.[3],[4],[5],[6],[7] In North India, a 1.38% incidence of canine anomaly was found where 0.93% were maxillary canine impaction and 0.37% were mandibular canine impaction.[8] Common theories contributing to the etiology of maxillary canine impaction are the guidance and genetic theories.[4],[9],[10] The guidance theory suggests that local mechanical factors interfere with the path of canine eruption as potential etiologies.[11] According to the genetic theory, impacted maxillary canines are conjointly associated with other genetic abnormalities such as submerged deciduous molars, hypoplastic enamel, mandibular premolar aplasia, and diminutive maxillary lateral incisors.[9],[10] If left untreated, it can lead to the formation of dentigerous cyst, root resorption of adjacent tooth, ankylosis of teeth, migration, and loss of arch space.[3] When intercepted early on time, the maxillary canine can be treated with extraction of deciduous canine and palatal expansion with anchorage from the deciduous molars whenever possible. At the later stages of development, the treatment of maxillary canine requires surgical exposure and orthodontic traction which is challenging both to patient and clinician and can require complex biomechanics and the use of mini-screws.[12] This would increase the treatment time and cost as compared to early intervention. It is, therefore, imperative to recognize the risk of canine impaction as soon as possible to intervene at an early stage and to prevent the establishment of full-blown case of impaction.[12]

Conventional two- and three-dimensional imaging is used in diagnosing the position and the excepted path of eruption of the permanent canines. They are also used to evaluate the growth, development, and morphometric relationships of craniofacial and dental structures. They also give diagnostic information about the variations related to the skull, cervical spine, including the abnormal sella turcica morphology, sella bridge occurring with craniofacial and dental deviations.[13],[14]

Sella turcica has a major importance in the field of orthodontics. The anterior contour of sella turcica is useful in predicting patient growth and in assessing the craniofacial morphology and superimposing serial cephalograms. Orthodontists should be familiar with the morphologic variations of sella turcica that will aid in diagnosing any underlying pathologies associated with it. One common morphologic variation of sella turcica is the presence of a sella bridge. This irregular bridge formation is the result of exaggerated ossification of the dura mater between the anterior and posterior clinoid processes of the sphenoid bone or abnormal embryologic development of the sphenoid bone.[4] The calcification of the sella turcica bridge might be positively associated with palatally displaced canine (PDC).[4],[12],[14],[15],[16] The reason might be that sella turcica, dental epithelial progenitor cells, and maxillary, palatal, and frontonasal developmental fields share a common embryologic origin (neural crest cells). In addition, genetic mutations might negatively influence the development of the midface, teeth, and parts of the sella turcica.[4],[12],[17],[18] Many prognostic factors[19] as well as skeletal features that can indicate a high risk of impaction have been studied.[20] The authors have found a relationship between palatally impacted canine and sella turcica bridging.[4],[7],[8],[21],[22],[23],[24] The anterior wall of sella shares a common embryological origin with the dental lamina which forms from the neural crest cells, and therefore, a common genetic origin of dental and sella anomalies is plausible.[12]


The aim of this study was to evaluate the relationship of sella turcica bridging in patients with palatally impacted canine.

  Materials and Methods Top

The study was conducted on 21 pretreatment lateral cephalograms of patients with palatally impacted canines (study group) aged between 14 and 28 years and 29 patients with normally erupted canines (control group) aged between 15 and 31 years who reported to and have undergone fixed orthodontic treatment in the Department of Orthodontics and Dentofacial Orthopedics, Bhojia Dental College and Hospital, Budh, Baddi, Distt. Solan, Himachal Pradesh. Each individual's basic information about name, age, and history including that of previous orthodontic treatment was taken from the department. Only those patients were included in the study that satisfied the following selection criteria.

Inclusion criteria (study group)

  1. Diagnosis of palatally impacted canine with any depth position or severity
  2. Full complement of teeth irrespective of third molars
  3. Any malocclusion (Class I, II, III)
  4. Radiographs with good hard and soft tissue outline.

Exclusion criteria (study group)

  1. Patients with craniofacial abnormality/syndromes.

The diagnosis of palatally impacted canine was based on clinical examination and confirmed by orthopantomography.

Angulation method was used which involves the use of a single panoramic radiograph to measure the angulation of the impacted maxillary canine with the occlusal plane [Figure 1]. If the angle formed by long axis of canine is >65°, the impacted tooth is considered as buccally, placed and if it is <65°, it is diagnosed as palatally impacted.[25] Additional intraoral periapical and occlusal radiographs were also taken for some patients.
Figure 1: Panoramic radiograph of a patient showing angulation method to determine the position of the canine

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The sample was divided into two groups [Table 1].
Table 1: Grouping of sample

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All the cephalometric radiographs were taken using standard procedure. A single investigator performed the cephalometric tracings on lead acetate tracing sheet. The landmarks [Figure 2] were identified and marked. Various sella measurements [Figure 2] were made on the cephalometric tracings.[7]
Figure 2: Sella landmarks and measurements. DS: Dorsum sellae, TS: Tuberculum sellae; (a) Interclinoid distance (sella length), (b) Sella diameter, (c) Sella depth

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Sella landmarks used in the study[7] [Figure 2]

  1. Tuberculum sellae (TS): The anterior border of the sella turcica
  2. Dorsum sellae (DS): The posterior border of the sella turcica.

Sella measurements used in the study[7] [Figure 2]

  1. Sagittal interclinoid distance/sella length (a): The distance between the tip of the DS and the TS
  2. Sella diameter (b): The distance between the tip of the TS and the most posterior point of the inner surface of the posterior wall of the sella
  3. Sella depth©: Line dropped perpendicular distance from sella length to the deepest point on the sella floor

To quantify the severity of bridging, the standard scoring scale developed by Leonardi et al.[14] was applied [Figure 3].
Figure 3: Sella turcica calcification showing types of bridging I (normal), II (partial calcification), III (complete calcification)

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  1. Type I – No calcification or bridging (normal sella): The interclinoid distance (sella length) was either equal to or greater than 3 quarters of the greatest anteroposterior diameter
  2. Type II – Partial calcification: The interclinoid distance was equal to or less than 3 quarters of the greatest anteroposterior diameter
  3. Type III – Complete calcification: Only the diaphragm sella was evident of the radiograph.

Statistical analysis

The values so obtained were subjected to statistical analysis. SPSS software was used. Kolmogorov–Smirnov test was used to check the normality of the data. Descriptive statistics (mean, standard deviation, Standard Error (SE), max, and min) for sella parameters were obtained for both the groups. To compare the sella parameters between the control and study groups, Mann–Whitney and Wilcoxon tests were used. Odds ratio was calculated to estimate the strength of association between sella bridging and impacted canines.

Error of measurement

Fifteen cephalograms were selected randomly and retracted to evaluate the intraoperator reliability and reproducibility of landmarks and reference planes for each of the groups evaluated.

  Results Top

The study was done to evaluate the relationship of sella bridging in patients having palatally impacted canine and in patients with normally erupted canine. The study included 21 pretreatment lateral cephalograms of patients with impacted canine and 29 patients with normally erupted canines. Various sella parameters (interclinoid distance, sella depth, and sella diameter) were measured for both the groups. One-sample Kolmogorov–Smirnov [Table 2] was applied to the whole sample and the parameters. It was found that the three variables (interclinoid distance, sella diameter, and sella depth) were not distributed normally, so nonparametric tests were applied (Mann–Whitney and Wilcoxon tests).
Table 2: One-sample Kolmogorov–Smirnov test

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The descriptive statistics of the three parameters for the control and study groups are depicted in [Table 3]. The mean value of interclinoid distance (4.02 ± 1.854 mm) and sella diameter (7.57 ± 1.77 mm) in the study group was less than in the control group's interclinoid distance (7.55 ± 1.67 mm) and sella diameter (9.60 ± 1.14 mm), whereas the mean value for sella depth was found to be similar between both the study group (6.81 ± 0.74 mm) and the control group (6.22 ± 1.11 mm).
Table 3: Descriptive statistics in study and control groups

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Since the three variables were not normally distributed, so Mann–Whitney and Wilcoxon tests were conducted to analyze the mean values of the variables by comparing the study and control groups [Table 4]. The results showed that there was a statistically significant difference between the sella diameter and the interclinoid distance (P < 0.001), whereas sella depth (P = 0.45) did not show any significant difference between the groups.
Table 4: Mann–Whitney and Wilcoxon tests to compare variables between study group and control group

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The highest frequency of calcification was of type II (61.9%), followed by type I (23.8%) and then type III (14.3%) in the study group, whereas most patients in the control group showed calcification type I (68.96%), followed by type II (31.04%). There was no incidence of type III (0%) calcification in the control group [Table 5]. Chi-square test was calculated to compare the degree of sella bridging in both the groups, and the calcification was found to be highly significant. The strength of the association between sella bridging and impacted canines was estimated by calculating the odds ratio. The odds of having partial and complete bridging among the patients were 7 times greater in the study group than in the control group (odds ratio, 7.11: confidence interval, 1.98–25.5)
Table 5: Degree of calcification in study and control groups

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  Discussion Top

Calcification of diaphragma sellae, which radiologically has been described as “roofing” or “bridging” of the sella, in the absence of clinical signs or symptoms, is considered a normal variant of the sella turcica, although many pathological processes can be associated with this calcification. It has been suggested that an interclinoid ligament is laid down in cartilage at an early stage of development and then ossifies in very early childhood. This ossification can be due to the complex embryology of the sphenoid bone. According to this theory, a sella turcica bridge should be considered a developmental anomaly. Moreover, as the area anterior to the sella turcica in the early embryonic period develops predominantly from neural crest cells, any structural deviations in the anterior wall are believed to be related to specific deviations in the facial skeleton.[14] The altered morphology of sella, anterior clinoid process, and sella length play a pivotal role in bridge formation. True bony union occurs at an early age. After that, changes are insignificant in sella length and sella bridge during the child matures.[7]

The study was focused on the dimensions of sella turcica and the association of sella bridging in patients with impacted canines in comparison to patients with erupted canines. The study consisted of pretreatment lateral cephalograms of 21 patients with canine impaction (study group) and 29 patients with normally erupted canine (control group) who were randomly selected from the department records. The cephalograms were hand traced for the landmarks and planes, and the sella dimensions were measured and compared between the study and control groups. The sella diameter and the interclinoid distance were found to be decreased in the study group, whereas the sella depth was found to be similar in both the groups. When the parameters were compared between the groups, they were found to be statistically significant for the sella diameter and interclinoid distance.

The standard scoring scale developed by Leonardi et al.[14] was used to measure the severity of bridging into three types, namely type I – no calcification, type II – partial calcification, and type III – complete calcification in the study and control groups. It was found that there was a greater frequency of type II and type III calcification indicating the presence of bridging in the study group when compared to the control group, and the difference was statistically significant.

This might be attributed to the shared embryogenic origin of sella turcica, many midface skeletal fields, and progenitor cells of the dental epithelium (neural crest cells) as well as shared genes involved in their development (e.g., HOX or sonic hedgehog genes).[4],[7] The sella turcica bridge might be more prevalent in patients with severe craniofacial deviations and tooth anomalies as well as other disorders and syndromes.[7] It might be positively associated with severe craniofacial deviation which would require combined surgical and orthodontic treatment protocols, or nevoid basal cell carcinoma syndrome along with calcification of the falx cerebri, or vertebral anomalies.[7] Leonardi et al.[14] found a significant association between sella bridging and dental anomalies such as PDCs, agenesis of second mandibular premolars, and dental transposition. Ali et al.[4] reported that the chance of observing increased calcification of the interclinoid ligament or sella bridging in patients with an impacted canine is four times higher than in patients without dental anomalies. Similar results were found by other authors, confirming the relationship between ossification of the interclinoid ligament and canine impaction.[4],[7],[14],[24]

The frequency of sella turcica bridging observed in the present study had a higher occurrence of full or partial calcification in the study group. The results were in accordance with the studies done by Najim and Al-Nakib,[16] Leonardi et al.,[14] Ali et al.,[4] Ghadimi et al.,[7] and Majeed et al.[24]

Thus, sella bridging highlights the risk of future palatal canine impactions, especially children having siblings or parents with canine impaction. The results of this study suggest that careful monitoring is needed for the eruption timing of the maxillary canines in people with calcified sella turcica. According to review of the literature, the prevalence of impacted canines might be greater in women compared to men.[7] However, further studies are required in this matter.

  Conclusion Top

The following conclusions can be drawn from this study, which inter-relates sella turcica bridging with impacted canines.

  1. The frequency of sella turcica bridging is increased in patients with canine impactions
  2. Sella turcica length (interclinoid distance) is reduced in patients with canine impactions
  3. The chances of having partial or complete bridging in patients with impacted canines are approximately 7 times greater than those with erupted canines.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Bishara SE. Impacted maxillary canines: A review. Am J Orthod Dentofac Orthop 1992;101:159-71.  Back to cited text no. 3
Ali B, Shaikh A, Fida M. Association between sella turcica bridging and palatal canine impaction. Am J Orthod Dentofacial Orthop 2014;146:437-41.  Back to cited text no. 4
Axelsson S, Storhaug K, Kjaer I. Post-natal size and morphology of the sella turcica. Longitudinal cephalometric standards for Norwegians between 6 and 21 years of age. Eur J Orthod 2004;26:597-604.  Back to cited text no. 5
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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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