|Year : 2018 | Volume
| Issue : 4 | Page : 423-426
Triple mental foramina: CBCT findings of an unusual anatomical variant
J John Hearty Deepak, A Nelson, C Saravana Bharathi, D Angeline Deepthi
Department of Oral Medicine and Radiology, Rajas Dental College and Hospital, Kavalkinaru, Tirunelveli, Tamil Nadu, India
|Date of Submission||14-Sep-2018|
|Date of Acceptance||13-Dec-2018|
|Date of Web Publication||17-Jan-2019|
Dr. J John Hearty Deepak
1 Vinayagar Nagar, Jeba Garden, NGO A Colony, Tirunelveli, Tamil Nadu - 627 007
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The mental foramen is an important anatomic landmark located on the buccal aspect of the mandible. Evaluation of anatomical variants in the mental foramen (MF) is an important prerequisite for implant and surgical procedures involving the anterior part of the mandible body to avoid mental nerve branches injury. The most frequent variation is the presence of double mental foramen, ranging from 1.4% to 12.5%. The incidence of triple mental foramen is extremely rare ranging from 0.7% to 1.2%. Cone beam computed tomography (CBCT) is the diagnostic tool of choice for imaging the maxillofacial region, which allows accurate three-dimensional analysis of mental foramen variations. The present report describes an unusual case of triple mental foramina of the right side of the mandible in a 39-year-old south Indian male detected by CBCT.
Keywords: Accessory mental foramen, anatomic variation, cone-beam computed tomography, mental foramen
|How to cite this article:|
Hearty Deepak J J, Nelson A, Bharathi C S, Deepthi D A. Triple mental foramina: CBCT findings of an unusual anatomical variant. J Indian Acad Oral Med Radiol 2018;30:423-6
|How to cite this URL:|
Hearty Deepak J J, Nelson A, Bharathi C S, Deepthi D A. Triple mental foramina: CBCT findings of an unusual anatomical variant. J Indian Acad Oral Med Radiol [serial online] 2018 [cited 2019 Apr 21];30:423-6. Available from: http://www.jiaomr.in/text.asp?2018/30/4/423/250251
| Introduction|| |
Mental foramen (MF) is located near the apices of the mandibular premolars. Double or multiple MF, termed as accessory mental foramen (AMF), with a rare prevalence of 1.4–10 and 0.7%–1.2% for triple MF. AMF occurs due to the splitting of the mental nerve into several fasciculi before the development of MF during the 12th week of intrauterine life. Assessment of AMF would prevent inferior alveolar nerve injuries during administration of local anesthesia, periapical surgery, and implant placement. Cone-beam computed tomography (CBCT) allows a comprehensive evaluation of AMF. This report describes the presence of unilateral triple MF detected by CBCT.,,,
| Case Report|| |
A 39-year-old male patient was examined by CBCT (NewTom GO 3D, Italy) as a part of implant planning. The scan was performed using a standard exposure and patient positioning protocol (90 kV, 2.4 s, 7 mA). The data were reconstructed at a voxel size of 0.1 mm. Triple MF was clearly evident on the right side of the mandible in cross-sectional and three-dimensional re-constructional images of CBCT. [Figure 1] shows the cropped three-dimensional reconstruction. Ovoid openings in the buccal cortex of the right mandible constituting well-defined three MFs along with nerve markings are visible. The third MF was small and distant to the other two MFs. [Figure 2] shows the cropped panoramic reconstruction of slice thickness of 1 mm exhibiting the branches of inferior alveolar canal into two in the region of 45, as well as continuation of the canal anteriorly. This section proved that there was a continuation of the inferior alveolar canal from the second MF anteriorly. [Figure 3] shows axial sections with slice interval of 2 mm showing the division of the inferior alveolar canal into two MFs. Further axial and sagittal sections were reconstructed to study the anatomy of the third MF. [Figure 4] shows the axial section in the apical region of 43 exhibiting the pathway of the third inferior alveolar canal opening as third MF. [Figure 5] shows series of sagittal section in relation to 43 showing the third MF. The distance between each foramen was calculated. [Figure 6] shows the axial section exhibiting the distance marked between the first and second MF and second and third MF.
|Figure 1: Cropped three-dimensional maximum intensity projection. Ovoid openings in the buccal cortex of the right mandible constituting well-defined three mental foramens along with nerve markings are visible|
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|Figure 2: Cropped panoramic reconstruction of slice thickness 1 mm showing branches of inferior alveolar canal into two in the region of 45 and continuation of the canal|
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|Figure 3: Axial sections with slice interval 2 mm shows the division of the inferior alveolar canal into two mental foramens|
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|Figure 4: Axial section in the apical region of 43 shows the pathway of the third inferior alveolar canal opening as the third mental foramen|
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|Figure 5: Series of sagittal section in relation to 43 shows the third mental foramen|
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|Figure 6: Axial section shows the distance marked between the first and second mental foramen and the second and third mental foramen|
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Finally, the width of each foramen were calculated in sagittal reconstructed sections. [Figure 7] shows series of sagittal section showing the measurements of maximum diameter of first, second, and third MF.
|Figure 7: Series of sagittal section shows the measurements of maximum diameter of the first, second, and third mental foramen|
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| Discussion|| |
Precise knowledge of vital anatomical structures emerging from MF is essential in local anesthesia administration, orthodontic mini-implant anchorage, dental implants, and other surgical entities. The position and number of MFs can vary among individuals, however, panoramic and intraoral radiographs cannot always demonstrate them. Variations in the number of foramina have also been reported, with more than one MF being present on one or more sides of the mandible. These additional foramina are called AMF. In the identification of anatomical variations, it is important to differentiate an AMF from a nutrient foramen. The AMF is an opening in the bone originating from a ramification of the mandibular canal, as observed in the present case. Conversely, the nutrient foramen does not originate in the mandibular canal and its dimensions are comparatively small. In our case, there were three MF on the right side of the mandible, which was noticed during a CBCT evaluation of the bone for an implant. The third MF was at the apical region of the canine at a long distance from the other two MFs. The dimensions of the major two mental foramen were 2.3 and 1.9 mm, respectively. On the basis of other studies,, We considered AMF to be the smallest among them. An AMF is usually less than 1.0 mm in size,, however in the present case, it was relatively wide, posing a greater risk of surgical complications in the region. The mean diameter of the MF is typically 3.0 mm, ranging from 1.8 to 5.1 mm. In the present case, both the MF were in the normal diameter range. Katakami et al. in a study of 150 patients observed the presence of 17 AMFs by CBCT, with 59% located posteriorly to the MF. Another study conducted on 157 patients demonstrated the presence of 15 AMFs, nine of which were located posteriorly to the MF., On the basis of these findings, the present study is contradictory to the literature because the AMF detected here were slightly located in an anterior direction with respect to the MF. Our case report was unique in such a way that the third MF was identified in CBCT, which was not at all seen in orthopantomogram. The mean diameter of the third MF was 0.7 mm, which was suggestive of AMF.
Katakami et al. and Naitoh et al. have reported studies that showed few cases with triple MF., In our case, all the three MFs were present on the buccal side of the mandible, which was correlated with the study done by Mihaylova. The third AMF was located at a distance of 10.6 mm away from the MF, which was not seen in any previous study. It was differentiated from nutrient canal, using CBCT nerve tracing procedure. Damage to neurovascular bundles may cause hemorrhage, paresthesia, or dysesthesia, among other consequences. Thakur et al. emphasized the importance of identifying the AMF before the treatment of neuralgia, because in patients with this variation, incomplete neurectomy of the mental nerve results in treatment failure and symptom recurrence. Kulkarni et al. reported a case in which the AMF and its nervous component were discovered accidentally during surgery because the presurgical panoramic radiography had not revealed any variation. Thus, a precise AMF analysis is only possible with CT/CBCT, which provides an image of better quality and lower distortion than conventional exams.,
| Conclusion|| |
This case report demonstrates that CBCT is a useful tool for the anatomic assessment of the MF region. It is essential to be aware of the possibility of these anatomical variations before planning surgery.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]