Mandibular canal
In human anatomy, the mandibular canal is a canal within the mandible that contains the inferior alveolar nerve, inferior alveolar artery, and inferior alveolar vein. It runs obliquely downward and forward in the ramus, and then horizontally forward in the body, where it is placed under the alveoli and communicates with them by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off a small canal known as the mandibular incisive canal, which run to the cavities containing the incisor teeth. It carries branches of the inferior alveolar nerve  and artery. It is continuous with the mental foramen (which opens onto front of mandible) and mandibular foramen (on medial aspect of ramus). Variations. The mandibular canal is fairly close to the apices of the second molar in 50% of the radiographs. In 40%, canal is away from the root apices, and in only 10% of the radiographs the root apices appeared to penetrate the canal. In root canal therapy of the second molar one should be cautious of over extending the reamer or the root canal filling materials because there is a possible risk of inferior alveolar nerve injury