|Year : 2018 | Volume
| Issue : 2 | Page : 133-135
The course of double mandibular canal - confront to dentist
Jayasheela Mallappa1, Neeharika Sree1, B H Dhanya Kumar2, Dhoom Singh Mehta1
1 Department of Periodontics, Bapuji Dental College and Hospital, Davangere, Karnataka, India
2 Department of Prosthodontics, Bapuji Dental College and Hospital, Davangere, Karnataka, India
|Date of Web Publication||18-Dec-2018|
Room No. 5, Department of Periodontics, Bapuji Dental College and Hospital, Davangere - 577 004, Karnataka
Source of Support: None, Conflict of Interest: None
The mandibular canal is usually a single canal 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. The identification of the mandibular canal and its anatomic variations is of great importance in many branches of dentistry, especially in implant dentistry. Sometimes, there may be variations in the normal anatomic structures; one of the rarest among them is double mandibular canal. The clinician should be aware of such variations to avoid complications during the treatment. In the present case report, we have discussed about a case with double mandibular canal and the complications that can arise during the treatment.
Keywords: Bone grafts, complications, dental implants, mandibular canal
|How to cite this article:|
Mallappa J, Sree N, Kumar BD, Mehta DS. The course of double mandibular canal - confront to dentist. Int J Oral Health Sci 2018;8:133-5
| Introduction|| |
The mandibular canal is usually a single channel, enclosed by bony tissue, forming an upward concave curve as the posterior part is descending and the anterior part is ascending. Its two ends are made up of two foramina as follows: the mandibular foramen at the back and the mental foramen at the front. It contains lower alveolar neurovascular bundle. When examined in different sections, it can vary in shape, being sometimes oval, circular, or pyriform. Radiographically, according to some authors, its appearance has been described as “radiolucent ribbon between two white lines,”, whereas others defined it as “dark linear shadow with thin radiopaque superior and inferior borders cast by the lamella of the bone that bounds the canal.” The mandibular canal transmits the inferior alveolar artery and the inferior alveolar nerve, to supply the teeth and adjacent structures. The existence of double mandibular canals has been determined from extraoral panoramic radiograph. Three inferior dental nerves form in the course of embryologic development to innervate each of the three groups of mandibular teeth. This development is followed in time by fusion of the nerves. This theory would explain the persistence in some patients with double mandibular canals, secondary to incomplete fusion of this nerves.,, In double mandibular canals, two separate mandibular canals are present, which originate at two mandibular foramina and terminate at two mental foramina. During surgical procedures involving mandible such as dental implant treatment, sagittal split ramus osteotomy, and orthognathic and reconstructive surgeries, a double mandibular canal can lead to many complications such as displacement of the third molar into the nerve canal during surgery, bleeding, and traumatic neuroma.,,, Our case is a unique one as it belongs to Type 2 in the classification of mandibular canal bifurcations given by Langlais et al. and the occurrence of 54.4% in the literature. Hence, to prevent these complications, a proper knowledge of the mandibular canal and its variations in position is very important.
| Case Report|| |
A 54-year-old female patient was reported with a chief complaint of loss of the teeth in the left and right, upper and lower back teeth region. The patient's medical and dental history was nonrelevant. The patient was interested in replacing her teeth with implants; hence, she was advised with routine blood investigations and panoramic radiographs. On examination of the panoramic radiograph, double mandibular canal was noticed on the left side. To know the course and for confirmation of the mandibular canals, the patient was sent for cone beam computed tomography (CBCT) [Figure 1] and [Figure 2]. On examination of the CBCT, the presence of the double mandibular canal on the left side was confirmed. Among the two canals, one canal was present at distance of 3 mm from the base of the mandible, and the other was present at a distance of 3 mm from the first canal. Both these canals are united at the mental foramen. With the assistance of the CBCT, we could trace the course of the canal and plan the treatment successfully. In this case, we could place fixed prosthesis since the patient was not willing for implant therapy due to the cost factor. We were able to avoid complications which could have happened during anesthesia. The patient was followed for 2 years with no apparent complications.
| Discussion|| |
For a surgical treatment to be successful, a thorough knowledge of anatomical structures is necessary. There are many anatomical structures left undiagnosed during the surgical procedures, one among them is double mandibular canal which may develop a lot of complications such as traumatic neuroma, bleeding, paresthesia, and inadequate anesthesia during the procedure.,,,
Recognition of variations in the mandibular canal is very important to prevent intra and postoperative complications.
Langlais et al. classified mandibular canal bifurcation into four types as follows:
- Type 1: Unilateral bifurcation extending to and bordering (surrounding area) the region of the third molar (1U). Bilateral bifurcation extending to and bordering (surrounding area) (1B) the region of the third molar
- Type 2: Unilateral bifurcation extending along the main canal and then coming together in the mandibular rami (2UR). Unilateral bifurcation extending along the main canal and then coming together in the mandibular body (2UC). Bilateral bifurcation extending along the main canal and then coming together in the mandibular rami (2BR). Bilateral bifurcation extending along the main canal and then coming together in the mandibular body (2BC)
- Type 3: Combination of the first two categories (Types 1 and 2)
- Type 4: Two channels originating from two distinct foramina and then joining to form a single, broad mandibular canal.
In the present case, the mandibular canal belongs to Type 4. There are many diagnostic aids available to recognize variations in mandibular canal such as orthopantomography (OPG), CT scan, magnetic resonance imaging (MRI), and CBCT. Among them, CBCT is considered more reliable because it produces clear images of the mandibular canal, free of overlapping and ghost images, and also with less exposure to radiation. It also helps to know density and the trabecular pattern of the bone. The presence of double mandibular canal was confirmed by CBCT which helped us to prevent the postoperative complications and to continue with the required treatment. During surgical procedures, if there is insufficient bone thickness, bone should be grafted to obtain the optimal thickness. During such cases, block graft or particulate bone grafts are used to increase the thickness of the bone. While harvesting block grafts in such conditions where one of the mandibular canals may be at the lower border of the mandible, there may be trauma to the mandibular canal causing paresthesia and traumatic neuroma. In cases of implant placement, care should be ensured to avoid impingement of the superior canal. The complete study of the mandibular canal is mandatory before any surgical intervention of the jaw is performed for the safety and betterment of the patient.
Thus before planning the treatment, proper history of the patient to be taken and required investigations to be performed to have a proper record of the patient and prevent complications during the treatment.
| Conclusion|| |
The presence of bifid mandibular canals is very common, yet it is important to recognize this anatomical variation in any surgical procedures involving the lower jaw. Its presence can be recognized by OPG, but its course and type of canal can only be confirmed by three-dimensional radiographs.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/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.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]