The bifid mandibular canal in three-dimensional radiography: morphologic and quantitative characteristics

The mandibular canal is a prominent anatomical structure and it is of great clinical importance since it contains the inferior alveolar nerve. The clinician is advised to proceed cautiously in the vicinity of the mandibular canal to avoid any damage to its neurovascular content. Based on observations in dry mandibles, in panoramic radiographs, and recently in three-dimensional radiography, various anatomical variations of the mandibular canals have been described. One such variant is the so-called bifid mandibular canal (BMC). Embryologically, multiple canals develop and subsequently fuse to form a single mandibular canal; however, occasionally fusion fails or is incomplete resulting in one or multiple BMCs. Clinically relevant issues with regard to the BMCs include hemorrhagic or neurological disorders following damage to these aberrant canals. This literature review presents morphological and quantitative data about BMCs from studies using three-dimensional radiography, i.e. CT and/or CBCT. The reported frequencies of BMCs per patient ranged from 9.8 - 66.5% and per mandibular side from 7.7 - 46.5%. Gender, age or side predilection is currently inconclusive with regard to the occurrence of BMCs. Various types of BMCs have been described in the literature, such as retromolar, dental, forward, or buccolingual canals. BMCs may originate from the mandibular canal along its entire course, but bifurcation appears to be more frequent in the posterior compared to the anterior canal portions. Mean BMC length was reported to range from 10.2 - 16.9 mm, and mean BMC diameter from 0.9 - 2.3 mm. In conclusion, the presence of a BMC must be taken into consideration for treatment planning and anesthetic, endodontic, or surgical interventions in the mandible.