Correlation of linear dimensions of sella turcica with anteroposterior skeletal jaw relationship of Egyptian subjects using CBCT

The aim of this retrospective study was to find whether there is a correlation between the linear dimensions of the sella turcica and different anteroposterior skeletal growth patterns in an Egyptian population using CBCT. CBCT radiographs of 129 adult patients (60 males, 69 females) were retrieved from the archive of the radiology department of the Faculty of Dentistry, Suez Canal University. They were divided into three groups according to sagittal growth pattern and the sella turcica length, depth and diameter were measured for each case. No statistically significant differences were found between all sella turcica measurements and the anteroposterior jaw relationship. The p-values were 0.087, 0.007 and 0.998 for the diameter, depth and length respectively. (64) Mohamed Adel Nadim E.D. J. Vol. 65, No. 1 Furthermore, Russell and Kjaer found an evident change of sella turcica shape prenatally and postnatally in children with fragile X and Down syndrome. (6) In the field of orthodontics it is sometimes insufficient to rely solely on the results of lateral cephalograms to discriminate facial skeletal types. In such cases knowledge about the relationship between shape and size of sella turcica and the type of facial skeletal class can help the orthodontist reach a definitive decision for treatment planning. (7) Several studies have been conducted to correlate the size and shape of the sella turcica and the anteroposterior relationship of the jaws in different populations using conventional lateral cephalograms. (8-10) From the abovementioned review it could be seen that the previous studies were conducted using lateral cephalograms and none to our knowledge was performed on an Egyptian sample. The aim of the present study is to find out whether there is a correlation between the size and shape of sella turcica and the sagittal relationship of the jaws in an Egyptian population using CBCT. MATERIALS AND METHODS The present retrospective study was conducted on the CBCT radiographs of 129 patients ranging in age between 20 and 40 years (60 males and 69 females). Radiographs of adults only were selected for the study because the morphology of sella turcica does not change significantly after the age of 12 years. (11) The radiographs were taken from the archives of the Oral Radiology Department Faculty of Dentistry, Suez Canal University. The selection criteria of the CBCT images were as follows: 1. High quality full skull CBCT images where the sella turcica appeared with maximum clarity. 2. The CBCT images were of subjects free from any craniofacial abnormalities. 3. No apparent pathology of the maxillofacial region. 4. No apparent facial asymmetry. 5. No significant anatomical variation in the sella turcica and sphenoidal regions. The CBCT images were performed using SCANORA 3DX scanner. (Scanora 3DX, Soredex, Finland). The field of view was fixed at 240x165mm for all images using standard resolution mode. The operating parameters were 90KVp, 10mA and the scan time was about 6 seconds. The voxel size was 0.5 mm using Flat panel a-Si detector. The acquired data was transferred into DICOM format, then exported into On Demand 3D application software (On Demand Cybermed. Co., Seoul, Korea) for image analysis and measurements. Using Dental 3D and dynamic light box display application, the linear measurements of length, depth, and diameter of the sella turcica were done using the method described by Silverman (12). The axial view at the level of the anterior nasal spine was used for all measurements taken from CBCT images. Subsequently, 1-mm sagittal slices, were made distal to (right side) of the midsagittal plane, for the measurement of the length, depth and diameter of the sella turcica. (Fig.1and 2). Fig. (1) The sella turcica length (1), diameter (2) and depth (3); TS — tuberculum sella; DS — dorsum sella; BPF — base of pituitary fossa [18, 36]. CORRELATION OF LINEAR DIMENSIONS OF SELLA TURCICA WITH ANTEROPOSTERIOR (65) The sella turcica length is defined as the distance between the tip of tuberculum s ellae and dorsum sellae. The depth is the deepest point of the floor of sella turcica, and the diameter is the furthest point on the posteroinferior aspect of the pituitary fossa to the most superior point on the tuberculum sella. Radiologic evaluations were performed by an experienced dento-maxillofacial radiologist. The intra-observer agreement was performed by reassessing the greater part of the images twice, with a 4-week interval between both viewings. Grouping of CBCT images: From the 3D reformatted CBCT images volumes were divided into three groups based on the ANB angle, the images were divided according to the sagittal skeletal dentofacial skeletal pattern: Class I (ANB; 2–4°), Class II (ANB; > 4°), and class III (ANB; < 2°). Statistical Analysis Numerical data were explored for normality by checking the distribution of data and using tests of normality (Kolmogorov-Smirnov and ShapiroWilk tests). Data showed normal (parametric) distribution. Data were presented as mean, standard deviation (SD) and 95% Confidence Interval (95% CI) values. One-way ANOVA was used to compare between the six groups. Bonferroni’s posthoc test was used for pair-wise comparisons. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM SPSS® Statistics Version 20 for Windows. RESULTS The mean and standard deviation and the results of one-way ANOVA test for comparisons between Sella Turcica measurements in the three groups are shown in table (1). No statistically significant differences were found between all sella turcica measurements and the anteroposterior jaw relationship. The p-values were 0.087, 0.007 and 0.998 for the diameter, depth and length respectively. Fig. (2) i) The blue line shows the midsagittal slice selected as a reference view for the measurement of length, diameter, and depth. ii) The reference lines used for measuring the sella turcica size on the midsagittal slice: a) bold line, length of sella; b) line, prebendicular to length depth of sella; c) diameter of sella. (66) Mohamed Adel Nadim E.D. J. Vol. 65, No. 1