|Year : 2021 | Volume
| Issue : 1 | Page : 32-39
Variations in anatomical landmarks of mandible using cone beam computed tomography - A cross-sectional study
Nitesh Tyagi1, Neelkant Patil1, Mohit Sareen1, Manoj Meena1, Supriya Rathore2, Shobhit Kaswan1
1 Department of Oral Medicine and Radiology, Rajasthan Dental College and Hospital, Jaipur, Rajasthan, India
2 Department of Dentistry, SMS Medical College, Jaipur, Rajasthan, India
|Date of Submission||10-Jul-2020|
|Date of Decision||13-Jan-2021|
|Date of Acceptance||13-Jan-2021|
|Date of Web Publication||26-Mar-2021|
Dr. Nitesh Tyagi
Department of Oral Medicine and Radiology, Rajasthan Dental College and Hospital, Ajmer National High Way-NH-8, Bagru, Jaipur, Rajasthan - 302 026
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Cone beam computed tomography (CBCT) is a diagnostic imaging modality for implant and surgical procedures in anterior and posterior mandibular area. It provides adequate information concerning maxillofacial regions, optimum image quality, excellent geometric accuracy, and low radiation dose. Aim: The aim of this study was to evaluate prevalence and anatomical variations in Mandible (Mandibular Incisive canal, Lingual Foramen, Mental Foramen, and Mandibular canal) in CBCT scans of the maxillofacial region. Methodology: All CBCT cross-sectional images of 40 study participants was analyzed for the presence of anatomical landmarks. All the anatomical parameters were compared with respect to age groups, dentition, gender, and right and left side and their respective distances from the inferior border of mandible and alveolar crest were measured using CS 3D imaging software (Kodak). Results: Lingual Foramen, Mental Foramen, and Mandibular Foramen were seen in all (100%) study samples, incisive foramen 83% and anterior loop in 25% of study samples. On statistical analysis, the difference of the mean distance of incisive foramen, mental foramen, anterior loop and mandibular foramen from lower border of mandible and alveolar crest was significant with relation to gender (P = 0.006) and with relation to dentate, partially dentate, and edentulous were found to be significantly different (P < 0.001). Conclusions: Careful assessment of the anatomical landmarks is essential to avoid neurosensory and bleeding complications using CBCT.
Keywords: Anterior loop, CBCT, incisive foramen, lingual foramen, mandibular foramen, mental foramen
|How to cite this article:|
Tyagi N, Patil N, Sareen M, Meena M, Rathore S, Kaswan S. Variations in anatomical landmarks of mandible using cone beam computed tomography - A cross-sectional study. J Indian Acad Oral Med Radiol 2021;33:32-9
|How to cite this URL:|
Tyagi N, Patil N, Sareen M, Meena M, Rathore S, Kaswan S. Variations in anatomical landmarks of mandible using cone beam computed tomography - A cross-sectional study. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Apr 14];33:32-9. Available from: https://www.jiaomr.in/text.asp?2021/33/1/32/312193
| Introduction|| |
Cone beam computed tomography (CBCT) is a diagnostic imaging modality that provides adequate information concerning the maxillofacial regions, optimum image quality and excellent geometric accuracy. Its low radiation dose coupled with the ease of handling, low cost accessibility makes CBCT as a suitable system for implant placement and surgical procedures in maxilla and mandible.
The CBCT software programs helps in evaluation of anatomical landmarks and its variations in axial, sagittal, and coronal planes.
Preoperative radiological examination by CBCT helps in assessing the apical bone height, buccolingual width, and angulations of the available bone.
Therefore, the present study was conducted to evaluate anatomical variations in anterior and posterior mandibular region which included Lingual canal and foramen, Mandibular Incisive canal, Anterior loop, Mental Foramen, and Mandibular canal on CBCT scans of maxillofacial region.
| Subjects and Methods|| |
This study was conducted in department of Oral Medicine and Radiology for the period of 6 months from February 2015 to August 2015. Brief dental and medical history was recorded followed by clinical examination. All the patients who required CBCT investigation and fulfilled the inclusion and exclusion criteria were included in the study and such patients were 40 in number belonging to age group of 20-60 years. Patients with periodontal diseases, partially and completely edentulous for implant planning, assessment of impacted teeth, and orthodontic evaluation were included. Patients with systemic diseases, trauma, bone disorders, congenital diseases, syndromes, benign and malignant tumors were excluded. All procedures performed in this study involving human participants were in accordance with the ethical standards of the Institutional ethical committee [Rajasthan dental college and hospital/Ethical/2014/2332, date 26/02/2014] and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Participants were briefed about the study and informed written consent was taken from each of them. All the exposure parameters were set according to the patient age, built and height and scout image was taken with pre-shoot button to check correct patient position followed by complete scan.
All CBCT images were taken on Carestream imaging system (CS 3D imaging) using FOV 17 × 11 cm image volume and reconstructed with isotropic 300 × 300 × 300 μm voxels. The tube voltage ranged from 68 to 90 kvp, tube current was 4 mA and an exposure time of 11.30 s was used. Tube voltage was altered depending upon the physique of patient and presence of metallic structures such as crowns, implants, etc. All CBCT scan cross-sectional images of 40 study participants taken from CBCT machine were analyzed by two observers. To eliminate inter observer variations, if a landmark was not seen by two observers it was considered as not seen. But if it is seen by two observers it is considered as to be present and average of measurement was kept as final reading.
All CBCT scan cross-sectional images were analyzed for the presence of lingual foramen, mandibular incisive canal, anterior loop, mental foramen and mandibular canal and their respective distances from the inferior border of mandible & alveolar crest were made using CS 3D imaging software. All measurements were made and compared on both right and left sides [Figure 1], [Figure 2], [Figure 3], [Figure 4].
The mandible of each patient was rotated with the occlusal plane parallel to horizontal plane and then further rotated with the mandible cantered on the mid-sagittal plane of the image and perpendicular to the occlusal plane. Subsequently, continual buccolingual (cross-sectional) images of mandible bone were created using the slice function of care steam software. The lingual foramen (lingual canals) and incisive foramen were searched in transformed images on the monitor, then the distance from alveolar crest and lower border of mandible were determined. The central bucco-lingual image of tooth (lower first molar) was selected to measure the position of the mandibular canal from alveolar crest and lower border of mandible.
The CBCT images were evaluated in coronal view and buccolingual (cross-sectional) distance from inferior margin of mental foramen and anterior loop from lower border of mandible and upper border from alveolar crest. For observing Anterior loop on each volume, the axial slices were reconstructed parallel to lower border of mandible.
Unpaired “t-test,” one-way “ANOVA test” with “POST-HOC TUKEY,” “HSD test” were used for analysis of continuous variables, whereas “Chi-SQUARE test” and “FISHER EXACT test” were used for categorical/numerical values.
Based on the findings of previous study, 95% confidence level and 80% power of study, sample size and all statistical analysis was done by using MEDICAL 188.8.131.52 version software. P value < 0.05 was taken as significant.
| Results|| |
Out of 40 study participants, there were 19 male (47.5%) and 21 female (52.50%), the study participants were divided into three age groups, 20–39 years, 40–59 years, and greater than or equal to 60 years. The sample was also evaluated as dentate (n = 17), partially dentate (n = 16), and edentate (n = 7). The lingual foramen, mental foramen, and mandibular foramen were seen in all (100%) study samples.
The mean distance of lingual foramen from alveolar crest was 17.8 ± 5.6 mm in males and 13.9 ± 3.82 mm in females [Graph 1] and from lower border of mandible was 11.2 ± 4.76 mm in males and 11 ± 3.72 mm in females [Table 1].
The second anatomical structure was incisive canal (IC). It was seen in 82.3% (78.95% were males and 85.71% were females) of cases. The distance of incisive canal was statistically significant from lower border of mandible on right and left side [Table 1] [Graph 1].
The third anatomical structure was anterior loop. It was verified in 25% cases [Table 2], in which male's showed higher incidence. There were statistically significant differences related to gender and the right and left side.
The fourth anatomical structure was mental foramen. The mean distance of mental foramen from alveolar crest and lower border of mandible on right side and left side in relation with age groups were found to be statistically non-significant [Table 3]. The mean distance of mental foramen from alveolar crest in dentate, partially dentate and edentulous were found statistically significant both on right (P > 0.001) and left side (P = 0.001) [Table 4], [Graph 2]. The distances of mental foramen from lower border of mandible on right and left side were not found to be statistically significant.
The last parameter observed was mandibular canal. The mean distance of mandibular foramen from alveolar crest in age group 20–39 years, 40–59 years, and 60 years were not significantly different on left side [Table 3], [Graph 3]. The mean distance measurements from alveolar crest were significantly different on right side to mandibular foramen were in dentate from edentulous and partially edentulous from edentulous [Table 4], [Graph 2]. The mean distance measurements from lower border of mandible were significant in males and females.
| Discussion|| |
The lingual foramen is situated in midline and branches of sublingual or sub-mental arteries exit from it. In the present study, lingual foramen was present in 100% of cases as was seen in studies conducted by Mehnaz et al. and Tagaya. In the present study, mean distance of lingual foramen from lower border of mandible was 11.2 ± 4.76 mm in males and 11 ± 3.72 mm in females. Similar results were seen in study conducted by Wane et al.
Incisive canal contains inferior alveolar nerve, travelling through a canal or through vacuoles in spongy bone mesially from the mental foramen.
In our study, incisive canal was seen in 82.3% (78.95% were males and 85.71% were females) of cases [Table 5]. These findings were in agreement with the results of Makis et al. (2010) and Rosa et al. (2013) who detected IC in 91% and 98.5% in their studies respectively using CBCT.,
In our study, the distance of incisive canal from lower border of mandible was 10.67 ± 2.8 mm on right side and 11.42 ± 2.3 mm on left side. Similar results were seen in study conducted by De Andrade et al. (2001).
Anterior loop was observed and verified in 25% cases, which was lower in comparison to study conducted by Lu CI et al. (2015). The presence of anterior loop of inferior alveolar nerve was found in 20% of cases in the study conducted by Chappidi V et al. (2019).,
In the present study, mental foramen was observed in all the cases. Similar findings were seen in studies conducted by F. Parnia et al, Jacob et al. The distance of mental foramen in dentate group was 12.5 mm, similar results was found in studies conducted by M. Shalash et al. & Kalen et al. but they have not compared between age groups.
When planning dental implant procedure, bone grafting, we should identify vertical mental foramen position, because after the extraction of teeth and because of the post extraction resorption seen in the alveolar bone, the mental foramen is closer to the alveolar crest. In extreme degrees of resorption, the mental nerve is found directly under the oral mucosa.
The last parameter observed was mandibular canal, its appearance is well defined radiolucent zone, lined by radiopaque borders in CBCT. Von Arx and Kurt reported disturbances of the inferior alveolar nerve including bleeding, and Silva et al. found complications because of sensory disturbances after mandibular ramus bone harvesting at a rate of 8.3%.
In our study, the mean distance from mandibular canal to alveolar crest in males was observed 16 ± 5.39 mm and 12.70 ± 3.99 mm in females. Comparatively these mean values were slightly lesser than 17.4 ± 3 mm as the values observed by Levine et al. This difference can be because of different racial population used in the study. Kivoner et al. observed the mean distance from alveolar crest is 14.16 mm and from lower border of mandible 12.54 mm.
In our study, the mean distance values were statistically significant in 20–39 years and it was also significant in left side in males (16.15 ± 5.39 mm) and females (12.70 ± 3.99 mm). Males have slightly higher values than females because of longer size of mandible.,
The CBCT provides multiplanner reconstructions and true-to-size images at very low radiation dosage, which enables excellent resolutions and good contrast for the visualization of these inter-foramina anatomical land marks.
Limitations and future prospects
Other variations including diameter and length of foramina, distances from buccal and lingual cortices of mandible, etc., should also be considered while electing to undertake any invasive procedures in the vicinity of these vital structures. One drawback of the present study was that the anatomical variations like shape and size could not be assessed. The minimalistic sample size and cost of the procedure prohibited from doing so. Studies with larger sample size that comprehensively evaluate the anatomical landmarks and their possible variations in the maxillofacial region should be considered to avoid postoperative surgical complications. Also, such assessments of anatomical landmarks should be done on a case-by-case basis to determine the exact location of each individual landmark.
| Conclusion|| |
The high detection rate of anatomical landmarks in mandible in CBCT shows high potential preoperative value of CBCT for surgical procedure. As the age progresses, there will be resorption of alveolar crest in cases of partially edentulous and edentulous condition, so in these kind of cases lower border of mandible will be helpful to locate the landmarks.
This data will help in preoperative implant planning, bone grafting, bone harvesting procedures by utilizing cross-sectional images and thus becomes mandatory for gaining supplementary information regarding variations in anatomical landmarks to avoid hemorrhage and neurosensory disturbances.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]