|Year : 2020 | Volume
| Issue : 1 | Page : 103-108
|Sexual dimorphism of mental foramen position in peruvian subjects: A cone-beam-computed tomography study
Yalil Augusto Rodriguez-Cardenas1, Manuel Casas-Campana2, Luis Ernesto Arriola-Guillén3, Aron Aliaga-Del Castillo4, Gustavo Armando Ruiz-Mora5, Maria Eugenia Guerrero6
1 Division of Oral and Maxillofacial Radiology, Faculty of Dentistry, Universidad Nacional de Colombia, Bogotá, Colombia
2 Division of Oral and Maxillofacial Radiology, School of Dentistry, Universidad Científica Del Sur, Lima, Perú
3 Division of Oral and Maxillofacial Radiology; Division of Orthodontics, School of Dentistry, Universidad Científica Del Sur, Lima, Perú
4 Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil
5 Division of Orthodontics, Faculty of Dentistry, Universidad Nacional de Colombia, Bogotá, Colombia
6 Medico Surgical Department, Faculty of Dentistry, Universidad Nacional Mayor de San Marcos, Lima, Perú
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|Date of Submission||10-Jul-2018|
|Date of Decision||09-Aug-2018|
|Date of Acceptance||24-Sep-2018|
|Date of Web Publication||02-Apr-2020|
| Abstract|| |
Background: The position of the mental foramen (MF) is particularly relevant in dentistry. The incorporation of new imaging techniques, such as cone-beam-computed tomography (CBCT), can be used to identify anatomic dimorphic traits. Aims: This study evaluated the sexual dimorphism of MF position by CBCT among a selected population. Methods: Fifty CBCT images from 20 to 40-year-old subjects (25 men and 25 women) were evaluated. The horizontal position was evaluated using the al Jasser-Nwoku classification to identify the position of the MF in the mandible. Two measurements were obtained on coronal sections to evaluate the vertical position of the MF: the distance from the uppermost alveolar ridge to the upper edge of the foramen and the distance from the inferior edge of the foramen to the lower border of the mandible. Statistical Analysis Used: Comparisons between sexes and sides were performed with Student's t-test and Chi-square tests. Results: The most frequent location of the MF was in line and below of the second premolar tooth in both men and women (P > 0.05). Additionally, significant differences were found between sexes for the distance from the inferior edge of the foramen to the lower border of the mandible in each side (P < 0.001 for the right and left sides). Conclusions: Horizontal position of the MF is not a sexually dimorphic feature and it is predominantly in line and below the second premolar tooth. Women present the MF in a more caudal position, closer to the mandibular base when compared to men.
Keywords: Body of mandible, cone-beam-computed tomography, sex characteristics
|How to cite this article:|
Rodriguez-Cardenas YA, Casas-Campana M, Arriola-Guillén LE, Aliaga-Del Castillo A, Ruiz-Mora GA, Guerrero ME. Sexual dimorphism of mental foramen position in peruvian subjects: A cone-beam-computed tomography study. Indian J Dent Res 2020;31:103-8
|How to cite this URL:|
Rodriguez-Cardenas YA, Casas-Campana M, Arriola-Guillén LE, Aliaga-Del Castillo A, Ruiz-Mora GA, Guerrero ME. Sexual dimorphism of mental foramen position in peruvian subjects: A cone-beam-computed tomography study. Indian J Dent Res [serial online] 2020 [cited 2022 Jan 22];31:103-8. Available from: https://www.ijdr.in/text.asp?2020/31/1/103/281820
| Introduction|| |
Human sexual dimorphism has been a frequent research topic in forensic medicine. Since the beginning of the last century, the finger length ratio was established as a sexual dimorphic trait, specifically between the index finger and the ring finger (2D:4D). This kind of differences is controlled by HOX 3 and HOX 4 genes as well as by the concentration of estrogen and testosterone in the uterus. Agnihotri et al. confirmed this difference for the Mauritian population. Mukhopadhyay studied morphometric traits in adult populations finding a strong sexual difference in the hyoid bone. Cavaignac et al. reported sexual differences regarding the distal portion of the femur using geometric morphometry.
In the dental field, Aggarwal et al. compared clinical and experimental methods for sex determination based on mandibular canines, and Alarcón et al. found sexual dimorphism in the mandibles of Spanish brachycephalic, dolicocephalic, and mesocephalic subjects using geometric morphometry. Zorba et al. reported sex-related differences on the mesiodistal width of permanent teeth, especially on the canine. They also reported a high sexual dimorphism level in Europeans, but a low one in South American populations.
This research topic is changing due to the incorporation of new imaging techniques, such as cone-beam-computed tomography (CBCT) that can be used to identify anatomic dimorphic traits. This new technique was applied by Tambawala et al. to evaluate sex-related differences in the foramen magnum and by Gamba et al. to find differences in five measurements describing the position of the mandibular canal in a Brazilian population. Sexual dimorphic traits were also found by Dong et al. in the mandibles of a Chinese population and by Gamba et al. in a Brazilian population.
The position of the mental foramen (MF) is particularly relevant in dentistry as this foramen is the exit of blood vessels and nerves from the skin and the oral mucosa tissue to the lower lip, cheeks, chin, and inferior teeth. MF has been studied by different available techniques: panoramic radiographs,, periapical radiographs,, magnetic resonance, multispiral computed tomography, high-resolution 3D ultrasound, and more recently by CBCT. Naitoh et al. evaluated the presence, but not the position, of an accessory MF in 157 Japanese subjects. They found a prevalence of 7% for the presence of accessory MFs, and an average distance of 6.3 mm between the MF and the accessory MF. Carruth et al. evaluated the shape and position of the MF by CBCT on 106 subjects. They found significant differences between sex and ethnic groups in North American populations. Chen et al. compared the distance between MF and the lower ridge of the jawbone on CBCT images. They reported that the MF location was lower in American than for Taiwanese populations.
The diagnostic and forensic value of CBCT is broadly acknowledged. This aspect might be highly relevant to identify the sex in human bones, as it is easy to locate and identify. But there are no previous studies neither about this topic nor about ethnic differences with South American populations.
Therefore, the objective of the present study was to evaluate the sexual dimorphism in the horizontal position of the MF (classified by al Jasser-Nwoku) and its vertical location in the mandible with respect to the alveolar upper ridge of the mandibular border on CBCT images from a Peruvian sample population.
| Methods|| |
This retrospective study was approved by the Ethics in Research Committee of the dental school. Fifty CBCT images from adults aged ≥20–41-year olds (25 men and 25 women) were selected for convenience from the record files of a diagnostic imaging center during the year 2014. The characteristics of the sample are summarized in [Table 1].
The inclusion criteria were CBCT images from healthy patients with no bone or dental losses, with presence of erupted lower bilateral premolars and molar teeth showing clear identification of the MF and with intact contact points between the neighboring teeth in order to guarantee the preservation of the upper alveolar ridge. Patients with mixed dentition, with presence of any hypodense or hyperdense structure next to the MF region, with craniofacial anomalies or syndromes, and with history of trauma or facial surgeries were excluded.
A minimum sample size of 20 participants per group was necessary to achieve 95% of test power, with a significance level of 0.05 to detect a difference between sexes of 2.12 mm for the distance from the inferior edge of the foramen to the lower border of the mandible, with a standard deviation of 3.45 mm (obtained from a previous pilot study).
All CBCT scans were obtained using Picasso Master 3D (Vatech Co., Ltd., Hwaseong, South Korea) set to 8 mA, 90 kV, and exposure time of 17.5 s, with a flat panel 25 × 20 cm, 30 × 30 cm, and a field of view of 8 × 8 cm, with a voxel size of 0.08 mm. The images were always obtained from patients in a seated position with the head position located by the device in such a way that the mid-sagittal plane was perpendicular to the floor plane and parallel to the Camper plane. The multiplanar reconstruction images were generated by the EZ Implant software (Vatech Hwaseong, Seoul, Korea) and were analyzed in a Samsung Intel Core i7-4770 workstation. Images were viewed in a dimly lit room on a 18-in monitor (Toshiba, Tokyo, Japan) set at a screen resolution of 1366 × 768 and 32-bit color depth.
The following parameters were applied to evaluate the CBCT images:
- MF position on the mandibular body evaluated on the volumetric reconstruction.
- This position was confirmed in a sagittal view under ray-sum projection, considering the longitudinal axis of the adjacent teeth. The al Jasser-Nwoku classification included the following options [Figure 1]:
|Figure 1: al Jasser-Nwoku classification adapted to ray-sum projection derived from cone-beam-computed tomography|
Click here to view
- Position 1: Anterior to first premolar
- Position 2: In line with first premolar
- Position 3: Between first and second premolar
- Position 4: In line with second premolar
- Position 5: Between second premolar and first molar
- Position 6: In line with first molar.
In the vertical measurement, in the event of finding a multiple foramen, the uppermost and lowermost points of them were considered according to Yosue and Brooks., In the horizontal evaluation, in the event of finding a multiple foramen, the biggest of them was taken as a reference point.
Then, a coronal, axial, and sagittal orientation was settled between those planes in such a way that they coincided with the center of the MF; on the coronal section, the MF vertical position was determined by the vertical measurement from the uppermost point of the alveolar ridge to its upper edge, and from the lower edge of the MF to the lowermost jaw basal point [Figure 2].
|Figure 2: Vertical measurements in the coronal plane for mental foramen location: distance from the uppermost alveolar ridge to upper edge of the mental foramen and distance from inferior edge of mental foramen to the lower border of the mandible|
Click here to view
The measurements were taken by an oral maxillofacial radiologist with more than 5 years of experience. Intra-examiner reliability was evaluated by the intra-class correlation coefficient, obtaining values greater than 0.9 for all measurements (95% confidence interval). Additionally, the Dahlberg's errors were smaller than 0.8 mm (0.5–0.8) for linear measurements. All variables were remeasured after a 30-day interval.
All statistical analyses were performed with the SPSS software v. 20 for Windows (IBM SPSS, Chicago, IL, USA). Normal distribution was assessed and confirmed with Shapiro–Wilk test. Then, parametrical statistics were applied to describe central tendency and data variability. Associations of the horizontal position of MF with sex were evaluated with the Chi-square test, and to compare the average vertical distance between sides and sexes, the t-test was applied. The statistical significance was set at P < 0.05 for all tests.
| Results|| |
In the horizontal evaluation, no statistically significant differences were found between sexes, and the commonest MF position for both men hemi-arcades was in line with the second premolar (P4) with 52% of the total sample, whereas in women, it was between the second premolar and first molar (P5), observed in 44% for the right side. In the left side, the most prevalent position was in line with the second premolar (P4) on 44% of the cases [Table 2].
In the vertical evaluation, no statistically significant sexual differences were detected for the uppermost alveolar ridge to the upper edge distance of the MF, either for the right or the left sides (P = 0.41 and P = 0.34, respectively [Table 3]).
Regarding the distance from the inferior edge of the MF to the lower border of the mandible, statistically significant differences were found in the right and left sides between sexes (P < 0.001 for the right and the left sides [Table 3]).
| Discussion|| |
Dimorphic skeletal traits include differences on the hyoid bone, the distal portion of the femur, the frontal outline bone, and other traits. However, ethnic differences may add difficulties in the analysis of sexual dimorphism. Therefore, it is necessary to specify the contribution of ethnic patterns to sexual dimorphism in specific population groups. The use of new imaging techniques, such as CBCT, may contribute to find new anatomic details for forensic human identification within specific ethnic and sex groups. Findings of sexual dimorphism on the foramen magnum in India, on the frontal sinus in Egypt, on the mandibular canal and jaw bones in Brazilian populations, are expressions of a new tendency in the local and worldwide research. This could be considered the first study in the field of forensic maxillofacial radiology that is performed in a contemporary adult Peruvian population to evaluate sexual dimorphism in the MF position.
The importance of the MF position for surgical maxillofacial procedures on the dental field, such as on endodontic microsurgery, dental implants placement, mentoplasty, and bone grafting, adds another dimension on this field of research. Concerning forensic applications, the advantage of sexual dimorphic traits in the mandible is related to its easy identification based on reproducible measurements such as those described in our study. Our results should be taken with caution, because of differences in techniques and interpretation criteria when comparing our results with other studies. On this regard, the results of this study can be compared only with the study of von Arx et al. that used a similar methodology.
Mental foramen Horizontal position
This is the most frequently measured anatomic landmark in previous studies using CBCT. In Swedish and Turkish populations, the MF most frequent position reported was between the two premolars (position P3 according to the classification used), with a prevalence of 56% and 59.8%, respectively. In our study, the MF was most frequently located bilaterally in line with the second premolar (P4, 52%) for men, and between the second and first premolar, in the right side (P5, 44%) and in line with the second premolar in the left side (P4, 44%) in women. Kalender et al. reported a higher percentage of the P3 position (between first and second premolars) for men on the right side (66.6%) than for women on the left side (59%).
Phillips et al. evaluated the MF position in cadavers and reported that 62.7% were positioned in line with the second premolar. The advantage of ex-vivo studies in cadavers is the anatomical accuracy. This study did not consider the premolar apex, as it was not visible in the cadaver. Therefore, intra-osseous anatomic references were not taken into account, whereas on CBCT, images are clearly visible. Differences among studies are related not only to differences in methodology but also to differences on the population. These studies' different results reinforce the concept of ethnic multifactorial variability. The present study contributes to prove this concept, emphasizing population differences and the need to define local morphological traits for human identification.
Mental foramen vertical position
Mental foramen distance to alveolar ridge
Haktanir et al. determined the MF position in 100 CBCT images from Turkish edentulous subjects. The average distance from the alveolar ridge to the upper edge of the MF was 14.2 mm (range: 10.7–29.8 mm), and they reported no significant differences between sides or sex. von Arx et al. reported an average value for the same distance of 12.6 mm (range: 5.7–19.6 mm). In our study, the average was 15.09 mm (range: 11.3–21.5 mm), similar to Haktanir et al. with no significant sexual dimorphism, but different to the one reported by von Arx et al. The mentioned average distance could be affected by the different bone loss scenario expected in some cases.
Mental foramen distance to the lower mandibular border
von Arx et al. reported an average of 13.2 mm for this distance, and no significant differences between sides, but with significant sexual dimorphism. Kalender et al. found an average of 12.4 mm, no significant differences between sides, and greater distance in men than in women. In the present study, the average was 13.86 mm, but with significant differences between sides. The MF is nearer to the mandibular border in women when compared to men mandibles. The greater distance difference in men is a constant report among studies and might be related to the smaller mandibular size in women than in men.,
The results of the present study provide an additional tool to evaluate human rests on forensic studies. The horizontal position of the MF in our study is predominantly in line with the second premolar, but it is frequently located between the second and the first premolar on the right side in women. This is a strong difference with other populations; however, it is not sexually dimorphic. Regarding the vertical position, the MF showed a more caudal and closer position to the mandibular border in women when compared to male mandibles and that the distance between the lower edge and the lower mandibular border presented sexual dimorphism in this population. The great ability to show 3D bone details on CBCT may promote the technique recommendation for maxillofacial forensic radiology. The authors suggest further studies using CBCT in other populations to increase the evidence provided by the results of the present study.
| Conclusions|| |
The horizontal position of the MF is not a sexually dimorphic trait. It is predominantly found in line and under the second premolar in both sexes. Regarding the vertical position, the MF is more caudal and closer to the mandibular base in women when compared to men mandibles.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Maria Eugenia Guerrero
Medico Surgical Department, Faculty of Dentistry, Universidad Nacional Mayor de San Marcos, Calle Germán Amézaga 375, Lima
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]
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