histological studies have shown that the inferior alveolar nerve typically courses through the mandible as one major trunk with branches extending to apices of the teeth . however , there are multiple smaller branches of the inferior alveolar nerve ( ian ) running roughly parallel to the major trunk such bifid canals are seen on panoramic and cone beam computed tomography ( cbct ) images . patients with bifid canals are at greater risk of inadequate anesthesia or difficulties with jaw surgery . even trifid mandibular canal has been reported . the major importance of location and configuration of mandibular canal variations is in the lower jaw surgeries , such as extraction of an impacted third molar , dental implant treatment , and sagital split ramus osteotomy . there are many causes of failure of ian blocks , including poor technique , anatomical variations , the presence of an acute infection , inability to enter the needle to the appropriate site or a reduced pain threshold . this case study focuses on one example of an anatomical variation : bifid mandibular canal ( bmc ) . when we reviewed the literature regarding bmc , we encountered only a few case reports that had two mental foramens . the following case report describes a patient with bilateral bmcs with two mental foramens by using cbct . a 47-year - old man was referred to his clinicians with persistent dull pain , 1 year after retrograde root canal treatment of tooth#24 . bifid mandibular canal with different patterns were located in each side of the jaw . while two mandibular canals with two distinct mandibular nerves ended to two different mental foramens in the left side [ figure 1 ] , in the right side the conjunction of two different mandibular canals ended to an isolated mental foramen [ figure 2 ] . cbct images of right mandibular canal , a : panoramic view , b : coronal view , c : sagittal - oblique view , d : crosssectional view . in the right side , the mandibular canal ended to two mandibular foramens and only one mental foramen cbct images of left mandibular canal , a , b : cross - sectional image , c : panoramic view , d : lateral sagittal , e : coronal view . in the left side , two mandibular canals including two mandibular nerves opened to two mental foramens the occurrence of bifid mandibular canal has been reported to be 0.35% by sanchis et al . , 0.8% by grover , 0.9% by nortje et al . , and 0.95% by langlais et al . reported that mandibular canal of specimen cadavers is not visible in 36.1% of panoramic radiographs . also , lindh et al . reported that the mandibular canal of specimen cadavers is clearly visible in almost 25% of panoramic radiographs . thus it was considered that there was a limitation in the observation of the mandibular canal by means of panoramic radiography . nowadays by the accurate new diagnostic equipments such as cbct , this statistics may increase . reported four cases of bmc by using cbct images that only two of them can be detected by panoramic radiography . cbct has enabled dentists to visualize the anatomy of the mandibular canal and ramified canals better than past . according to these finding and our observation , we suggest that cbct is more useful than conventional radiography such as panoramic images in detection of bmc . the first included bmcs extending to the area surrounding the third molar or to the tooth itself ; the second included bmcs arising from the same foramen but forming two separate canals which rejoined to form a single canal anteriorly ; the third type included a combination of the first two types ; and the last type included two radiographically separate canals with separate origins that eventually fused into a single canal anteriorly . nevertheless , the fact that , as opposed to the upper canals , the duplicate canals on the left side extended into different mental foramen allows us to consider this case as a new division . it is believed that one of the reasons that previous studies could not identify this type was using conventional radiographies and subsequently failing in detection narrow second mental foramen . the most common and first complication of bifid canal may appear in performing mandibular nerve block . the responsible nerve maybe long buccul or accessory ian . conventionally , anesthesia of the ipsilateral lip , chin , and teeth is indicative of an effective ianb . if a patient experiences only soft tissue anesthesia around the injection site , but not of the ipsilateral lip or chin , then a problem with local anesthesia technique is likely to be the cause of the failure . however , if there is soft tissue anesthesia of the lips and chin but not the teeth , one should consider anatomical variation . when dentists encounter this situation , if their problem is only inadequate anesthesia they should use another technique for local anesthesia . but if the surgical process must be done in this region , the anatomical variation of ian must be evaluated with diagnostic images . the best diagnostic imaging modality is cbct that has considerable benefits , such as low dose , appropriate cost , and well visual quality . the most common and first complication of bifid canal may appear in performing mandibular nerve block . the responsible nerve maybe long buccul or accessory ian . conventionally , anesthesia of the ipsilateral lip , chin , and teeth is indicative of an effective ianb . if a patient experiences only soft tissue anesthesia around the injection site , but not of the ipsilateral lip or chin , then a problem with local anesthesia technique is likely to be the cause of the failure . however , if there is soft tissue anesthesia of the lips and chin but not the teeth , one should consider anatomical variation . when dentists encounter this situation , if their problem is only inadequate anesthesia they should use another technique for local anesthesia . but if the surgical process must be done in this region , the anatomical variation of ian must be evaluated with diagnostic images . the best diagnostic imaging modality is cbct that has considerable benefits , such as low dose , appropriate cost , and well visual quality . bifid mandibular canal may exist in each patient . to manage this anatomic variation , dentists should choose appropriate images and local anesthesia technique .