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 Table of Contents  
Year : 2022  |  Volume : 8  |  Issue : 1  |  Page : 1-5

Evaluation of frontal sinus index in establishing sex dimorphism using three-dimensional cone beam computed tomography in Northern Saudi Arabian population

1 Department of Preventive Dentistry, College of Dentistry, Jouf University, Sakaka, Kingdom of, Saudi Arabia
2 Department of Oral Medicine and Radiology, College of Dentistry, Jouf University, Sakaka, Kingdom of, Saudi Arabia

Date of Submission06-Apr-2021
Date of Decision23-Sep-2021
Date of Acceptance27-Sep-2021
Date of Web Publication17-Mar-2022

Correspondence Address:
Radhika Doppalapudi
Department of Oral Medicine and Radiology, College of Dentistry, Jouf University, Sakaka
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jfsm.jfsm_19_21

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Purpose: Identification of sex of unknown people becomes important in situations of mass disaster. Previous studies have shown that morphological characteristic of frontal sinus is distinctive to particular individual and hence, literature suggests that it can be used in establishing identification of a person. However, few researches have concluded that, its use in determining sexual dimorphism is limited. Aim: This study aimed to evaluate frontal sinus index using cone beam computed tomography (CBCT) and differentiate sex dimorphism based on the index obtained. Materials and Methods: A retrospective cross-sectional study was undertaken using three-dimensional-CBCT scans. By simple random sampling method, 150 scans were selected, out of which 74 were of male and 76 were of female within the age group of 20–64 years. The frontal sinus width and the height were measured, and the ratio was taken as frontal sinus index. This index was correlated to the differentiation of sex. Data were analyzed using SPSS, and sex dimorphism was assessed using discriminant function analysis. Results: The mean height of the frontal sinus in both males and females was 30.12 ± 7.6 mm and 30.14 ± 7.8 mm, respectively. The mean width of frontal sinus in males (13.39 ± 3.6 mm) was slightly more than that of females (12.06 ± 3 mm). Conclusion: The parameter frontal sinus index measured using CBCT was found to be a contributing factor in sex determination in forensic identification within the sample population.

Keywords: Discriminant function analysis, forensic anthropology, frontal sinus index, sex dimorphism, three-dimensional cone beam computed tomography

How to cite this article:
Rao KA, Doppalapudi R, Al-Shammari NT, Patil S, Vundavalli S, Alam MK. Evaluation of frontal sinus index in establishing sex dimorphism using three-dimensional cone beam computed tomography in Northern Saudi Arabian population. J Forensic Sci Med 2022;8:1-5

How to cite this URL:
Rao KA, Doppalapudi R, Al-Shammari NT, Patil S, Vundavalli S, Alam MK. Evaluation of frontal sinus index in establishing sex dimorphism using three-dimensional cone beam computed tomography in Northern Saudi Arabian population. J Forensic Sci Med [serial online] 2022 [cited 2022 Aug 16];8:1-5. Available from: https://www.jfsmonline.com/text.asp?2022/8/1/1/339791

  Introduction Top

The identification of an unknown individual subjected to mass disaster through the human remains could be performed by several methods such as fingerprint, DNA analysis, and various other anthropological methods.[1],[2],[3],[4] During such investigations, if the soft tissues of human remnants have become putrid or are burnt, or in case, if the DNA is severely degraded, it becomes extremely difficult to carry out the fingerprint identification and DNA analysis.[5],[6] As a result, to identify the remains and ascertain an individual, it becomes essential to adopt various other anthropological methods. In such scenarios, the use of radiographs as an important tool for personal identification becomes crucial.[7],[8],[9],[10] In particular, the utility of three-dimensional cone beam computed tomography (3D-CBCT) under these circumstances renders better visualization of the region of interest over the conventional two-dimensional radiographs by avoiding the superimposition of structures beyond the plane of interest and also allowing the visualization of small differences of density. In addition, it improves the accuracy as the craniometric points that are used in the analysis can be precisely located and measured.[11] For the purpose of human identification in postmortem cases, Schuller (1921) was the first person to utilize the morphology of frontal sinus. It was his study, which highlighted the information about the frontal sinus with regard to its distinctiveness in shape, complexity, and individuality. Subsequently, quite a few authors based on the uniqueness of frontal sinus have used it for various forensic purposes.[7],[8]

Anatomically, the frontal sinuses are air-filled cavities situated between the external and internal cortical plates of the frontal bone. Each frontal sinus opens into corresponding middle meatus via the infundibulum. They are not obvious at birth. Their development starts during the second year of life. They are also not visible radiographically until the age of 5 years. It is widely acknowledged that their development gets completed by about 20 years of age. They remain constant until further expansion of the chambers, which happens as a result of bone resorption during advanced age.[12],[13]

Various in-depth studies have shown that frontal sinus reveals considerable disparities in relation to its shape, volume, and irregularity in different individuals. Owing to its asymmetrical shape along with its unique individual characteristics, even to monozygotic twins, it has become one of the most interesting and significant landmarks in numerous forensic identifications. The literature suggests that the frontal sinus can be used reliably in human identification, provided both antemortem and postmortem radiographs of the victims are available.[8],[9],[10],[11],[12]

By using logistic regression model in sex determination, Camargo et al. studied the morphology of frontal sinus in the radiographs of Brazilian population and found an accuracy rate of 79.7% in determining the sex dimorphism.[13] A study conducted to determine frontal sinus index for sex determination in the Indian population using lateral cephalometric radiographs showed significant differences in frontal sinus measurements with an accuracy of 67.59% in the differentiation of males and females.[14] Similarly, Motawei et al. conducted a study on the CBCT images of 53 subjects belonging to the Egyptian population and the frontal sinus measurements were correlated for sex differentiation. The results of their study showed significant differences with an accuracy of 76.7%.[15]

A comprehensive search of existing literature, however, did not reveal any studies considering the sex determination utilizing frontal sinus morphology among the Northern Province Saudi Arabian population. However, in the paucity of such studies in this population, the present study was conducted to determine the reliability and accuracy of the frontal sinus index as a method for sex identification using 3D-CBCT scanner.

Aims and objectives

  • Evaluate the frontal sinus index using CBCT
  • To differentiate sex dimorphism based on the frontal sinus index measurements obtained using CBCT.

  Materials and Methods Top

This retrospective, cross-sectional study included the analysis of a total of 150 patients who underwent 3D-CBCT scans for various other ailments in our institute from July 2017 to December 2017. The sample size was decided to be at least 150 considering 95% CI and 80% power, which is based on the recommendations of Hair et al., in which at least 50 samples are needed for each independent variable in multiple discriminant analysis.[16] The subjects were selected after reviewing the complete patient history and consisted of individuals belonging only to the Saudi Arabian population, residing in the Northern Province of the Kingdom.

After procuring the institutional ethical clearance from the Local Committee of Bioethics with the reference number 07-03-5/38 from Jouf University, KSA, the scan databases were analyzed. Out of 150 scans, 74 were of male and 76 were of female, in the age range of 20–64 years with a mean age of 32.5 years.

The exclusion criteria were based on the history of previous orthodontic treatments, patients with sinus pathologies such as mucosal thickenings or any masses in the sinuses, patients with a history of head trauma/fractures or surgeries including the orthognathic surgeries, and images with excessive artifacts in the anatomical field of interest.

All the scans were selected from the database of head-and-neck 3D-CBCT explorations which had a similar standardized protocol of acquisition and were attained using Cranex (SOREDEX, Tunusula, Finland) with an imaging protocol or field of view measuring 16 cm diameter × 13 cm height, 0.25-mm slice thickness, and a scanning time of 20 s. The measurements on the images were carried out in the accompanying SOREDEX software provided along with the device.

The linear measurements included for the analysis were the maximum height (MH) and the width of frontal sinus, which were calculated by measuring the maximum distance between two highest points in the mid-sagittal plane of frontal sinus images. The MH was measured between the highest (H) and the lowest points (L) of the frontal sinus by joining them. Similarly, maximum width was ascertained by connecting the anterior wall of the frontal sinus at its deepest portion to the MH line through a perpendicular line [Figure 1]. Based on these dimensions, the sinus index that is the ratio of height and width of the frontal sinus for each case was calculated.[14],[17],[18] The parameters to acquire the necessary data were measured by drawing the lines on the internal contour of the frontal sinus. Two independent observers carried out the measurements at varying intervals to assess the accuracy of measurements, and these values were in turn subjected to coefficient correlation test to rule out the intra- as well as inter-observer variability. The Cohen's Kappa measure of agreement showed that the interexaminer reliability was 0.82, whereas the intraexaminer reliability for investigator 1 and investigator 2 were 0.86 and 0.84, respectively.
Figure 1: Three-dimensional cone beam computed tomography image of frontal sinus in sagittal plane

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Statistical analysis

The collected data were analyzed using Statistical Software for Social Sciences (SPSS Version 20, IBM Corp., Chicago, USA). Descriptive statistics were done initially, and independent samples t-test was used to compare the mean values between males and females. Discriminant function analysis was used for sex prediction, binary logistic regression was done to identify odds ratio for each variable, and P ≤ 0.05 was considered as statistically significant for all comparisons.

  Results Top

[Table 1] describes descriptive statistics for height and width of frontal sinus in both males and females. The mean height of the frontal sinus in both males and females was 30.12 ± 7.6 mm and 30.14 ± 7.8 mm, respectively. The mean width of frontal sinus in males (13.39 ± 3.6 mm) was slightly more than that of females (12.06 ± 3 mm).
Table 1: Discriminant analysis of various parameters of frontal sinus

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The Box's M statistics was applied to check the validity of frontal sinus measurements in sex prediction. The results indicated that sex can be predicted using these two variables, which is statistically significant (P = 0.000) [Table 2].
Table 2: Box's M statistics for sex identification

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Unstandardized coefficient values obtained from canonical discriminant function coefficients [Table 3] were used in sex prediction. The estimated sex was calculated using the following equation: n = −9.96+ (-−0.378 × Ht. of frontal sinus) + (0.979 × width of frontal sinus) + (3.58 × ratio).
Table 3: Canonical discriminant function

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The sectioning (Eigen) value for sex prediction was 0.321, indicating that if the calculated value is 0.321 or above, then that skull belonged to males, whereas for females, it was below 0.321 [Table 3].

Using the height, width, and ratio of frontal sinus, we could correctly classify 63.1% of the total cases [Table 4].
Table 4: Prediction accuracy

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Binary logistic regression was performed to find the most contributing factor in sex prediction among the parameters evaluated, and it was found that height was a better indicator than other measurements of frontal sinus, which is statistically significant [Table 5].
Table 5: Binary logistic regression

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  Discussion Top

In the field of forensic science, personal identification especially in the cases of mass disasters, becomes very crucial. The four main features to establish the biological identity of an unknown individuals include age, sex, stature, and ethnic or the racial background. Out of these four features, sex determination can be done through various morphometric and nonmorphometric parameters. In some instances, where there is severe decomposition or severely burnt soft-tissue remains associated with degradation of DNA, the skeletal remains can aid in establishing the biological identity with the help of radiographs. The human maxillary sinuses were used for sex determination using panoramic radiographs by Queiroz et al., in which they concluded that the height and width of the maxillary sinus of men are greater when compared with those of women.[19] As accuracy becomes a pivotal instrument, the use of 3D-CBCT over the conventional 2D radiographs becomes essential. Numerous studies on the skeletal remains have so far emphasized that the radiological evaluation of skull, pelvis, and femora is very useful for the determination of sex. However, at certain circumstances, when just the skull bone or fragments of skull bones are found at the site of mass disaster, it is only the craniometrical features that will assist in sex identification.

The frontal sinuses are radiologically evident at 5 or 6 years of age and become completely developed and attain the maximum dimension by approximately 20 years of age and remain unchanged till late adulthood, except under rare circumstances such as fractures, tumors, or severe infections. Owing to its substantial variations in morphology with regard to the area and symmetry, the analysis of its measurements makes it a parameter of great importance to determine the sex dimorphism.

One among the earliest reports published on British population by Buckland-Wright states that the frontal sinuses in “males were approximately twice as large as the females.”[20] In contrast, the univariate statistical study conducted by Yoshino et al. based on the anteroposterior radiographs found no significant sexual dimorphism.[1]

Studies conducted by Lee et al., Mathur et al., Jhonson et al., and Ponde et al. found that greater dimensions in most measurements of frontal sinus were associated with male population, which is synchronous with the present study too.[21],[22],[23],[24] The discriminant statistics applied in our study for the measurements showed that the mean width of frontal sinus was more in the male population (13.39 ± 3.6 mm) as compared to that of the female population (12.06 ± 3 mm) [Table 1]. However, there was not much statistically significant difference in the comparison of mean height of frontal sinus between the two categories of the population.

Studies conducted by Yoshino et al. and Goyal et al. reported statistically insignificant differences between the sex dimorphism and frontal sinus measurements.[1],[25] On the contrary, the statistically significant result (P = 0.00) of Box's M statistics [Table 2] obtained in our study was encouraging as it indicated that sex could be predicted using the parameters mentioned. Furthermore, Goyal et al.'s study suggested that frontal sinuses may have limited application as a sole predictor of sex and ascribed their findings of low sex dimorphism to high interindividual differences in the morphology of sinuses and the modality of imaging which they used were based on simple 2D radiographs.[25] Nevertheless, in the current study, based on the discriminant function analysis, the prediction accuracy result [Table 4] showed that 63.1% of the cases could be correctly categorized. This could be attributed to the fact that all the pictures used were of extremely good-quality 3D-CBCT images. This was in tandem with the CBCT study conducted by Hamed et al., wherein an overall accuracy of 67% was reported in frontal sinus examination to identify sex.[11] These results are indicative of the fact that the examination of frontal sinus using CBCT can give more accurate results for identifying sex.

All the parameters analyzed were also subjected to binary logistic regression analysis [Table 5], which indicated that the height was a better indicator in sex prediction, which collaborated with the findings of Beladavar et al. on Indian population.[26] In addition, the statistical test of Canonical discriminant function [Table 3] in our study highlighted that the Eigen value for sex prediction can be set at 0.321, based on which, if the measurements are equal to or above the given value of 0.321, it would be indicative of the male population and in case if the calculated value is below the set limit, it will be suggestive of female population.

  Conclusion Top

The 3D-CBCT techniques incorporating greater accuracy rates and easy reproducibility procedure for frontal sinus examination can be suggested for sex determination in a forensic background.

The discrepancies between the accuracy percentages of identification between various studies can be attributed to various factors including the sample size and use of different equipment and techniques. It also highlights that other factors such as geographic, functional, age, hormonal, and craniofacial configurations have to be taken into consideration for each specific population. Based on measurements or dimensions calculated through various approaches, a population-specific equation should be generated while correlating the frontal sinus dimensions for predicting sex.


There is a need for standardizing the frontal sinus measurements and also the scope to report the error rates of various techniques. In many countries, especially in developing nations, the antemortem frontal sinus imaging is not routinely practiced. These inadequacies can make frontal sinus method for identification of sex inadmissible in the court of law. In certain circumstances, where the frontal sinus is affected by diseases, trauma, or surgery, other available evidences need to be used in the determination of sex.


The authors would like to thank Dr. Bader K Alzarea Dean, College of Dentistry, Jouf University, Sakaka, AlJouf, KSA.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Yoshino M, Miyasaka S, Sato H, Seta S. Classification system of frontal sinus patterns by radiography. Its application to identification of unknown skeletal remains. Forensic Sci Int 1987;34:289-99.  Back to cited text no. 1
Cameriere R, Ferrante L, Mirtella D, Rollo FU, Cingolani M. Frontal sinuses for identification: Quality of classifications, possible error and potential corrections. J Forensic Sci 2005;50:770-3.  Back to cited text no. 2
Cameriere R, Ferrante L, Molleson T, Brown B. Frontal sinus accuracy in identification as measured by false positives in kin groups. J Forensic Sci 2008;53:1280-2.  Back to cited text no. 3
Christensen AM. The impact of Daubert: Implications for testimony and research in forensic anthropology (and the use of frontal sinuses in personal identification). J Forensic Sci 2004;49:427-30.  Back to cited text no. 4
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Pfaeffli M, Vock P, Dirnhofer R, Braun M, Bolliger SA, Thali MJ. Post-mortem radiological CT identification based on classical ante-mortem X-ray examinations. Forensic Sci Int 2007;171:111-7.  Back to cited text no. 9
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Hamed SS, El-Badrawy AM, Fattah SA. SEX identification from frontal sinus using multi-detector computed tomography. J Forensic Radiol Imaging 2014;2:117-20.  Back to cited text no. 11
Cristiane RR, Nader W. Anatomo-radiological and morphometrical study of the frontal sinus in humans. Braz J Morphol Sci 2004;21:53-6.  Back to cited text no. 12
Camargo JR, Daruge E, Prado FB, Caria PH, Alves MC, Silva RF. The frontal sinus morphology in radiographs of Brazilian subjects; its forensic importance. Braz J Morphol Sci 2007;24:239-43.  Back to cited text no. 13
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Motawei SM, Wahba BA, Aboelmaaty WM, Tolba EM. Assessment of frontal sinus dimensions using CBCT to determine sexual dimorphism among Egyptian population. J Forensic Radiol Imaging 2016;6:8-13.  Back to cited text no. 15
Hair JF, Black WC, Babin BJ, Anderson RE. Multiple Discriminant Analysis; Text Book on Multivariate Data Analysis. 7th ed. New Jersey: Prentice Hall; 2010. p. 245-60.  Back to cited text no. 16
Benghiac AG, Thiel BA, Haba D. Reliability of the frontal sinus index for sex determination using CBCT. Rom J Leg Med 2015;23:275-8.  Back to cited text no. 17
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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