|Year : 2013 | Volume
| Issue : 2 | Page : 67-69
Trifid mandibular nerve canal
Mehmet Z Adisen, Melda Misirlioglu, Selmi Yilmaz
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Kirikkale University, Kirikkale, Turkey
|Date of Web Publication||21-Oct-2013|
Mehmet Z Adisen
Kirikkale University, Faculty of Dentistry, Department of Oral and Maxillofacial Radiology, Kirikkale
Source of Support: None, Conflict of Interest: None
The location and configuration of the mandibular canal are important in surgical procedures involving the mandible. Bifid mandibular canal (BMC) and trifid mandibular canal (TMC) are variations of the normal anatomy. In the literature, occurrence of TMC is much rarer than BMC that only a few cases have been reported. These variations can be detected on a panoramic radiograph however more precise information about the course of the mandibular canal can be revealed on cross-sectional tomographic images. This paper presents a rare case of TMC evaluated by panoramic radiograph and CBCT. The main purpose of this case report is to pay attention to an apparently harmful anomaly, which can induce complications while surgical procedures.
Keywords: Bifid mandibular canal, cone-beam computed tomography, mandibular canal variations, panoramic radiography, trifid mandibular canal
|How to cite this article:|
Adisen MZ, Misirlioglu M, Yilmaz S. Trifid mandibular nerve canal. J Oral Maxillofac Radiol 2013;1:67-9
| Introduction|| |
The mandibular canal (MC) is a usually single canal within the mandible that begins with mandibular foramen on the medial surface of the ascending mandibular ramus. It transmits the inferior alveolar artery, vein, and the inferior alveolar nerve. ,,,
MC is of particular interest to all who work in the field of dental surgery for obvious reasons, because it is important to detect the location and configuration of the MC in surgical procedures, including the extraction of an impacted third molar, dental implant treatment, sagittal split ramus osteotomy, and orthognatic and reconstructive surgeries. ,,,
Anatomical location and configuration of MC have been studied by several researchers and some variations of the MC, including bifid mandibular canals (BMC) and trifid mandibular canals (TMC), have been reported. ,,,,,, A review of the available literature revealed that the occurrence of BMC is unusual but is not rare as being thought. , On the other hand the occurrence of TMC is much rarer so that only a few cases have been reported. ,
BMC and TMC can be detected on panoramic radiographs. However there are obvious limitations in identifying the occurrence of multiple canals via the observation of two-dimensional (2D) images. Cross-sectional tomographic images perpendicular to the alveolar ridge provide the best information regarding the mandibular canal and its precise course. ,, Recently, cone-beam computed tomography (CBCT), with high-level spatial resolution, has been used for diagnostic imaging of the oral and maxillofacial regions and various anatomical structures. ,,
This paper presents a rare case of TMC which incidentally detected on sagittal and coronal planes of CBCT images.
| Case Report|| |
A 63-year-old man presented at our department for a dental implant evaluation. The patient had no history of systemic diseases. On the routinely performed panoramic radiograph unilaterally BMC was suggested on the left side [Figure 1]. Also multiple bilateral radiopaque lesions were detected in the area of the posterior ascending ramus. CBCT images were obtained from both sides of the jaw to identify the calcifications and determine potential implant sites in mandible. Pax Uni 3D (Vatech, Seoul, Korea) was used to capture CBCT images at the following settings: 50-90 kVp, 4-10 mA, 10 seconds exposure and 50 × 50 mm FOV size.
|Figure 1: (a) Cropped panoramic radiograph demonstrating the bifid mandibular canal on the left side. (b) Schematically drawing of the bifid mandibular canal|
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Two oral radiologists evaluated the CBCT images on the three plane of views (coronal, sagittal, and axial) using Ez3D2009 software. The density and contrast of images were adequately adjusted to clarify multiple canals. TMC was detected in CBCT images on the left side [Figure 2].
|Figure 2: CBCT images of the patient showing trifid mandibulary canal on (a) coronal, (b) sagittal, and (c) 3D views. The arrows show the accessory canals|
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While the panoramic radiography revealed one accessory canal at the left side, CBCT images localized two accessory canals in sagittal and coronal planes. Also the calcifications were diagnosed as tonsilloliths in palatal tonsils with CBCT images. The patient was informed of the presence of that unusual structure and referred to the Department of Oral and Maxillofacial Surgery for implant treatment.
| Discussion|| |
It is important for clinicians to recognize the presence of multiple canals on panoramic radiographs and modify the dental treatment accordingly. However panoramic radiographs suffer from severe limitations with the inherent errors of a 2D representation of a three-dimensional (3D) structure being distortion, magnification, and superimposition of the anatomical structures. Therefore the exact location and configuration of MC can only be identified with tomographic imaging. ,
Recently, CBCT has been introduced in an effort to compensate the shortcomings of the conventional CT, such as the higher radiation dose, lower spatial resolution, and the higher costs. , The CBCT is able to detect narrow canals, which may not be detected by panoramic images. It is also a recommended technique for detailed preoperative evaluation of multiple MCs. 
In panoramic image surveys, the occurrence of BMC presence was reported to be very low and ranged from 0.08 to 0.95%. ,,,,,, On the other hand in CBCT surveys, BMC has been reported to show prevalence rates ranging from 15.6 to 65%. , These results show the limitations of panoramic radiography in identifying the occurrence of BMC.
In the literature, occurrence of TMC is much rarer than BMC so that only a few cases have been reported. The first established case of the TMC was presented in a study with dry mandibles. , Apart from that there is only one case report showing unilateral TMC on CBCT images. 
Chavez et al. suggested that during embryonic development there may be three inferior dental nerves innervating three groups of mandibular teeth and later they fuse to form a single nerve. This theory would explain the existence of multiple canals resulting from the incomplete fusion of these nerves.
The location and configuration of MC variations has important clinical implications, because severe complications including unexpected bleeding, paraesthesia and traumatic neuroma may occur during surgical procedures involving the mandible. ,, Also inadequate anesthesia may be possible especially when two mandibular foramens are involved. ,, Furthermore, in cases of trauma, all mandibular fractures should be handled with care to ensure that the neurovascular bundle is lined up exactly to avoid impingement when the fracture is reduced. Additionally patients with mandibular prostheses may experience discomfort because of the pressure placed on the neurovascular bundle in the retromolar area. ,
It can be concluded that awareness and detection of multiple canals are of considerable interest to the general dentists to avoid complications during surgery. Initial screening for the presence of multiple canals can be executed by conventional panoramic radiography. However more precise information can be achieved with using CBCT scan with high-level spatial resolution.
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[Figure 1], [Figure 2]