This study aimed to evaluate and compare the bridging and dimensions of the sella turcica and calcification of the ponticulus posticus in subjects with different dental anomalies.
Pretreatment records of orthodontic patients with palatally impacted canines (n = 95), mandibular second premolar agenesis (n = 45), maxillary lateral incisor agenesis (n = 75), tooth transpositions (TT, n = 25), peg-shaped maxillary lateral incisors (n = 30), and third molar agenesis (TMA, n = 145) were analyzed and compared with the control group (CG) consisting of 145 subjects with skeletal Class I malocclusion and no dental anomalies. The length, diameter, and depth of the sella turcica were calculated for each patient. The degree of sella turcica bridging was scored as type I, II, and III, whereas the extent of ponticulus posticus was classified as Class I, II, and III.
Only decreases in the length and diameter of the sella turcica in subjects with TT were found to be statistically significant. Although type II bridging frequency was found to be significantly lower in subjects with mandibular second premolar agenesis, maxillary lateral incisor agenesis, TT, and TMA, type III bridging frequency was found to be significantly higher only in subjects with TMA. The decrease in Class I calcification frequencies and the increase in Class II calcification frequencies were found to be significant in subjects with palatally impacted canines, TT, and TMA compared with the CG. In addition, the presence of Class III calcification was found to be significantly more frequent in subjects with TMA than in the CG.
Although type II and type III bridging frequencies were found to be higher than in previous studies because of the higher type II bridging frequency in the CG, type II bridging frequency was found to be insignificant. Furthermore, an increased frequency of ponticulus posticus calcification was observed in subjects with palatally impacted canines, TT, and TMA.
The length and diameter of sella turcica were smaller in those with tooth transposition.
Type II bridging frequency was lower in those with dental anomalies.
Type III bridging frequency was higher in subjects with third molar agenesis.
Increased Class II calcification frequency was associated with some anomalies.
Class III calcification was more frequent in subjects with third molar agenesis.
Lateral cephalometric radiographs, which are routinely used in orthodontics for diagnosis, treatment planning, and skeletal maturation evaluation, could also provide other diagnostic data relating to the skull, face, and upper cervical spine. , The relationships between dimensional and morphologic variations in the sella turcica and various syndromes and disorders, , skeletal patterns, , and dental anomalies , , have been investigated in previous studies using lateral cephalograms.
Sella turcica is a saddle-shaped bony structure anatomically located in the intracranial surface of the body of the sphenoid bone. , From anterior to posterior, it consists of 2 anterior clinoid processes, tuberculum sella, pituitary fossa covered by diaphragma sellae, and 2 posterior clinoid processes. Because of abnormal development of the anterior and posterior clinoid processes, these bony structures may fuse and form osseous bridges. , In addition, the anterior and posterior walls of the sella turcica have been observed to have different embryologic developmental origins. Although the cartilage forming the posterior wall develops in the same way as the corpora of the vertebra under the direct influence of the notochord, the anterior wall develops from the neural crest cells. ,
Dental epithelial progenitor cells and maxillary, palatal, and frontonasal developmental fields share a common embryologic origin with the anterior wall of the sella turcica, which is the predominant derivative of neural crest cells. , Neural crest cells influence neck and shoulder development, sella turcica calcification, and tooth formation and eruption. , From this point of view, the morphologic variations and appearance of the sella turcica, which are established early in embryonic development, , may be associated with dental anomalies. , , ,
One of the cervical vertebral anomalies that can be observed in lateral cephalometric radiographs and are related to the activation of neural crest cells during fetal development is the calcification of the ponticulus posticus (atlantooccipital ligament or arcuate foramen). , This is described as an anomalous malformed bony bridge between the posterior section of the superior articular process and the posterolateral section of the superior margin of the posterior arch of the atlas. ,
Although the association between the dimensions and bridging of the sella turcica in patients with palatally impacted canines, , , tooth transpositions, and agenesis of the maxillary lateral incisors and the mandibular second premolar , has been investigated in some studies, no study has investigated its association with the peg-shaped maxillary lateral incisors and third molar agenesis (TMA). Furthermore, the calcification of the ponticulus posticus has been investigated only in subjects with palatally impacted canines. ,
In light of this information, the aims of this study were as follows: (1) to investigate the bridging and dimensions of the sella turcica and calcification of the ponticulus posticus in subjects with different dental anomalies, which are genetically determined and conjointly associated with each other, such as palatally impacted canines, tooth transpositions, peg-shaped maxillary lateral incisors, and agenesis of the maxillary lateral incisors, mandibular second premolars, and third molars , ; and (2) to compare these findings with the results for subjects with skeletal Class I malocclusion and no dental anomalies. The null hypothesis was that there is no correlation between the bridging and dimensions of the sella turcica and calcification of the ponticulus posticus and dental anomalies in orthodontic patients.
Material and methods
This case-control retrospective study was conducted in accordance with the ethics defined in the Declaration of Helsinki, and approval was obtained from Van Yüzüncü Yıl University, Faculty of Medicine, Research Ethics Committee (09.05.2018/11).
After detailed scanning of the last 5 years of digital archives from the Department of Orthodontics at the University of Van Yüzüncü Yıl, pretreatment records of 95 subjects with palatally impacted canines, 45 subjects with mandibular second premolar agenesis, 75 subjects with maxillary lateral incisor agenesis, 25 subjects with tooth transposition, 30 subjects with peg-shaped maxillary lateral incisors, and 145 subjects with TMA were selected. In addition, 145 subjects with skeletal Class I malocclusion and no dental anomalies were randomly selected from the digital archives and examined as the control group (CG). Attention was paid to match the chronological age of the study population and CG. The descriptive statistics of the groups that consisted of Turkish subjects are shown in Table I .
|Groups||Subjects, n||Age, y , mean ± SD||P value ∗||Female, n||Male, n||P value ∗|
|Palatally impacted canines||95||16.08 ± 3.10||0.207||76||19||0.028|
|Mandibular second premolar agenesis||45||15.60 ± 2.92||0.994||24||21||0.089|
|Maxillary lateral incisor agenesis||75||15.84 ± 3.37||0.570||52||23||0.001|
|Tooth transposition||25||15.81 ± 3.16||0.735||14||11||0.277|
|Peg-shaped maxillary lateral incisors||30||16.51 ± 2.85||0.108||18||12||0.437|
|TMA||145||16.37 ± 3.39||0.154||98||47||0.999|
|CG||145||15.59 ± 2.82||98||47|
Diagnoses of the dental anomalies were made using pretreatment panoramic and lateral cephalometric radiographs, intraoral photographs, and orthodontic dental casts. In subjects with palatally impacted canines, other diagnostic records such as cone-beam computed tomography recordings were also used. The number of dental anomalies was recorded.
The inclusion criteria were as follows: no previous orthodontic treatment or surgery, an age range of 13-21 years, good quality of lateral cephalometric radiographs and dental pantomograms, and clear visualization of the sella turcica and ponticulus posticus. The exclusion criteria were as follows: the presence of cleft lip or palate, craniofacial anomalies, syndromes, systemic disorders, and severe mandibular deviation and history of facial trauma, head and/or neck surgery, radiotherapy, and chemotherapy. The inclusion and exclusion criteria were the same for the study population and CGs.
The NemoCeph NX 2005 (Nemotec, Madrid, Spain) computer analysis program was used for the measurement of length, diameter, and depth of the sella turcica from lateral cephalometric radiographs. All the tracing and measurements were performed by 1 observer with 7 years of orthodontic experience (Y.K). After calibration of the radiographic images, cephalometric tracings were performed. Four points were determined on the sella turcica contour by the program: tuberculum sella (TS), dorsum sella, the farthest point on the inner wall of the sella, and the deepest point of the sella floor. The dimensions of the sella turcica were calculated using these 4 points: sella length, TS − dorsum sella; sella diameter, TS − farthest point on the inner wall of the sella; and sella depth, the distance of a line dropped perpendicularly from the interclinoidal distance to the deepest point of the sella floor ( Fig 1 ).
To quantify the degree of sella turcica bridging, the standardized scoring scale developed by Leonardi et al was applied. If the length of the sella turcica was equal to or greater than three fourths of the diameter, the sella was scored as type I (no calcification); if it was less than or equal to three quarters, the sella was scored as type II (partial calcification). When only the diaphragm sella was evident on the radiograph, it was scored as type III (complete calcification) ( Fig 2 ).
As the next step, the extent of ponticulus posticus calcification on the atlas was evaluated as Class I (no calcification: no bony emergence was observed), Class II (incomplete calcification: partial bony emergence was observed), or Class III (complete calcification: compete bone bridge was observed) ( Fig 3 , Supplementary Material ).
To evaluate the intraobserver error rate, 50 lateral cephalometric radiographs were randomly selected and measured by the same observer (Y.K) 2 weeks after the initial tracing. This random measurement error was calculated by applying Dahlberg’s formula. It was observed that these error values ranged from 0.13 mm to 0.36 mm, and the experimental error was considered unlikely to bias the accuracy of the sella measurements.
Because the standard deviation (σ) ranged from 2.14 to 3.43 in the results of a previous study, it was taken to be 2.5 for this study. Furthermore, for the 0.05 type I error rate, the z value and the effect size was assumed to be 1.96 and 1, respectively. On the basis of this information, the necessary sample size was found to be a minimum of 24.01 (≅24) according to the equation for sample size calculation (n = z 2 σ 2 /d 2 ).
The descriptive statistics for the continuous variables were presented as mean, standard deviation, minimum and maximum values, and percentages for categorical variables. A 1-way analysis of variance was used to compare the group means. A chi-square test was performed to determine the relationship between the categorical variables. In addition, a z test was used for the comparison of the proportions of the groups. All statistical analyses were carried out using SPSS software (version 22.0; IBM, Armonk, NY), and the level of statistical significance was set at 5%.
The lengths, diameters, and depths of the sella turcica in subjects with dental anomalies and the CG are shown in Table II . When compared with the CG, only decreases in the length and diameter in subjects with tooth transposition were found to be statistically significant. For the remaining linear measurements, no significant differences were found between the subjects with dental anomalies and the CG.