Association of sella turcica bridging and morphologic characteristics with palatally impacted canine in lateral cephalograms.

INTRODUCTION: Researchers have been interested in the rela’onship between sella turcica bridging and various dental anomalies. This study inves’gates the associa’on of sella turcica bridging and morphologic characteris’cs with the palatally impacted canine tooth. MATERIALS AND METHODS : Orthodon’c records with high-quality lateral cephalometric and panoramic images were chosen. The study comprised 30 pa’ents with palatally impacted canines (17 females and 13 males) and 30 controls with erupted canines (15 males and 15 females). The measurements were performed using the SCANORA 5.2.6 soKware. Further, the relevant data was collected and analyzed using SPSS soKware version 22. Descrip’ve sta’s’cal analysis was used to inves’gate data aKer their valida’on, with t-tests and chi-square tests to compare the two groups. The regression test was used to lessen the eﬀects of confounding variables. RESULTS: In the study group, 5 pa’ents had type III sella turcica bridging, whereas 2 pa’ents in the control group had type III sella turcica bridging. Results showed a sta’s’cally signiﬁcant diﬀerence between the two groups (P-value=0.017). In the study group, the interclinoid distance and canine tooth angle were signiﬁcantly lower than the control group (P-value=0.001, P-value=0.001). However, there were no signiﬁcant diﬀerences in the depth and anterior-posterior diameter of sella turcica between the two groups (P-value=0.543, P-value=0.766). In terms of age (P-value = 0.400) and gender (P-value = 0.605), there was no signiﬁcant diﬀerence between the two groups. CONCLUSION: The palatally canine impac’on may be associated with the bridging of the sella turcica. Therefore, sella turcica bridging can be used as a diagnos’c parameter for palatally canine impac’on.


Introduction
Sella turcica, an important anatomical landmark in lateral cephalometric imaging, is an area in the form of a saddle that is based in the middle part of the cranial fossa [1]. It is also an important finding for orthodontists since many pathological processes are shown by changes in the form and dimensions of the sella turcica. sella turcica is classified into three groups: circular, oval and flat shapes. The most common among them is the circular, followed by oval and flat respectively. [2]. Sella turcica bridging could be a common variation of sella turcica, possibly related to numerous systemic developmental syndromes [3]. According to the theories expressing that mutations of the HOX hedgehog gene negatively affect the midface, teeth and part of the sella turcica development, any modifications in the developmental level could result in sella turcica bridging that might further cause dental anomalies [4]. Dental anomalies can be caused by various factors, including genetic, epigenetic, and environmental influences [5]. Although many studies have been conducted on the common occurrence of various dental irregularities, few have looked into the connection between bridging of the sella turcica and dental anomalies [6].
Canine impaction is one of the types of dental anomalies. For many years, orthodontists have struggled with canine impaction. Examinations can be an effective way to reduce the cost and treatment time of the patients [7]. Excluding the third molars, the maxillary canine is the most commonly impacted [8]. Furthermore, impaction is more common in women [9]. Canine impaction in about 15% of cases is located buccally while in about 85% it is located palatally [10]. Buccal canine impaction is originally caused by dental crowding [11]. While palatally canine impactions frequently, but not always, are found in dentitions with various anomalies [12].
Some studies claim that sella turcica bridging is more common in patients with impacted canines [7,13], while others claim there is no significant link between impacted canines and sella turcica bridging [14,15].
As there are few studies about the association of sella turcica bridging and morphologic characteristics with canine impaction as well as contradictory comments. further studies are needed [16]. Therefore, this study aims to determine sella turcica morphologic characteristics and the possible relationship between the sella turcica bridging and the palatally canine impaction in lateral cephalometric radiographs.

Material and Methods
This retrospective case-control study with convenience sampling evaluated 30 patients (17 females and 13 males) with at least one palatally impacted maxillary canine compared with 30 patients (15 females and 15 males) with normally erupted canines matched in terms of age and gender. This study was conducted to determine the association between palatally canine impaction and sella turcica bridging using orthodontic patients' pretreatment radiographic records referred to private oral and maxillofacial radiology centers in Zanjan city (Iran), from 2017 to 2020, with an equal racial background as Iranian root. Approval from the Ethics Committee of Zanjan Dental school was obtained (number IR.ZUMS.REC.1398.417). All the patients who participated in the study signed written informed consent.
The inclusion criteria were 13-30 years old orthodontic patients with good quality standardized panoramic and lateral cephalograms were included in the study. Patients who had dental malformations and syndromes, significant illnesses or medical conditions as well as cases with blurred radiographic appearance and a history of orthognathic surgery, orthodontic treatment, cleft lip and palate, maxillofacial pathology, trauma were excluded from this study. The study group consisted of 30 patients (17 females and 13 males) with at least one palatally impacted maxillary canine and the control group of 30 patients (15 females and 15 males) with normally erupted canines no dental abnormalities. The two groups were matched in terms of age and sex. (Table 1) The pretreatment orthodontic panoramic and lateral cephalometric radiographs were used to diagnose tooth impaction or eruption [18]. To determine the palatally impaction of canine teeth, panoramic and lateral cephalometry radiographs and all other sources of information available, such as cone beam computed tomography, occlusal view radiographs were used, in some cases referring to orthodontic diagnostic records. The radiographic parameters studied were the interclinoid distance (the distance between the tip of the tuberculum sellae and the dorsume sellae), sella turcica depth (the length of a line dropped perpendicularly from the line above to the deepest point on the sella floor), anteroposterior diameter of the sella turcica (the longest distance between the tip of the tuberculum sellae and the posterior contour of the sella), sella turcica bridging and canine angle. The SCANORA 5.2.6 software was used to conduct measurements. The line drawn from the highest point of the condyles was used to compute the canine angle. (Figure 1) A standard scoring scale devised by Leonardi et al was used to assess the degree of sella turcica bridging [19]. Type I: normal sella turcica, interclinoid distance equal to or greater than three-quarters of the largest anteroposterior diameter. Type II: incomplete calcification, interclinoid distance equal to or lower than three-quarters of the largest anteroposterior diameter. Type III: complete calcification, only the sella turcica diaphragm is visible on radiography. (Figure 2) Lateral cephalometric radiographs were used to assess the sella turcica, performed by an expert oral and maxillofacial radiologist. To confirm the accuracy of the measures, 10 samples were re-examined at twoweek intervals to ensure the reliability and reproducibility of the assessments. No significant difference was found (P-value>0.05). The intraclass correlation coefficient (ICC) is presented in the table 2. SPSS software version 22 was used to analyze data. Descriptive statistical analysis was utilized and to compare the two groups, t-test and chi-square tests were performed.

Results
A total of 60 radiographic records of patients were investigated. To assess data distribution, Kolmogorov-Smirnov test was employed. The results of the normality test showed normal distribution (P-value>0.05). We used t-test, two groups proportion and chi-square test to compare the data between two groups.   Associa'on of sella turcica bridging and morphologic characteris'cs with palatally impacted canine in lateral cephalograms. In the study group 20 patients had unilateral and 10 patients had bilateral canine impaction. While the total occurrence of canine impaction in maxillary left and right side was 54.5% (n=12) and 45.5% (n=10) in female respectively, this was 55.6% (n=10) and 44.4% (n=8) in male (Z=0.06, P-value=0.949).
The measures of study group's interclinoid distance was significantly shorter than the control group (Pvalue = 0.001) as well as the canine angle which was significantly lower in the study group. (P-value = 0.001). However, the depth of the sella turcica and anteroposterior diameter of sella was not significantly different between the two groups with P-value 0.543 and 0.766, respectively. (Table  3)

Discussion
The sella turcica is a structure that may be easily traced in cephalometric analysis and may be seen clearly on lateral cephalometric radiographs. The shape of the sella turcica is very important in orthodontics because it serves as a reference point in orthodontic analysis [20].
We opted to investigate the association between sella turcica bridging and canine impaction and compare it to normal canine eruption due to the importance of its characteristics, such as morphology and size, as factors that can alter the pituitary gland's pathologic status. The results of this study revealed that patients with canine impaction had considerably higher sella turcica bridging. Furthermore, the interclinoidal distance and canine angle of the study group were significantly lower than those of the control group. The depth of the sella turcica and the anteroposterior width of the sella turcica did not differ significantly. The findings of this investigation were in line with the majority of previous studies [7,13,19].
In line with the present study, Dadgar et al.(2020) conducted a study in 46 patients with canine impaction and 46 patients with normal canine eruption. The results showed that palatal canine impaction is positively associated with both atlas arcuate foramen and sella turcica bridging. However, the arcuate foramen was not investigated, but morphological characteristics of sella turcica were defined in the present study [13].
In the Baidas et al.(2018) study there was no difference in the morphology of the sella turcica between patients with and without canine impaction. The incidence of sella turcica bridging was observed to be considerably greater in patients with canine impaction (P-value 0.0001) [19].   Associa'on of sella turcica bridging and morphologic characteris'cs with palatally impacted canine in lateral cephalograms. were consistent with the current study, revealing that the incidence of sella turcica bridging was considerably higher in the study group than in the control group (P value = 0.001). In addition, the sagittal interclinoidal distance was significantly reduced. (P value=0.028) [7]. Leonardi et al. (2006) also studied 34 individuals with maxillary impacted canine anomalies and determined that there is a relationship between impacted canine and sella turcica bridging, although there are no significant differences based on age or gender [6]. In this investigation as well, we observed no significant association between age and sex. The scope of our research was constrained by a few variables. The study used lateral cephalograms, which are a two-dimensional representation of a threedimensional subject with its own set of landmark recognition and tracing errors. Due to the COVID-19 pandemic, few patients were involved in our study, but although it resulted in a smaller sample size, this sample size was adequate to obtain proper test power in terms of most variables which were investigated in this study. Further studies in larger communities with different ethnic backgrounds and more thorough examination of the patient's profile (e.g., height, BMI, family history, underlying condition, etc.) and using cone beam computed tomographic records instead of lateral cephalometric records are recommended.

Conclusion
The results showed that the incidence of sella turcica bridging was greater in individuals with maxillary canine impaction than in the control group. In addition, the interclinoidal distance and canine angle were lower in the study group than in the control group, despite the fact that the depth of the sella turcica and the anteriorposterior diameter of the sella turcica were not substantially different.
As a conclusion, palatally canine impaction may be related to the bridging of the sella turcica. Therefore, sella turcica bridging can be used as a diagnostic parameter for palatally canine impaction.