Observation of the internal structure of the mandible related to implant placement in the mandibular anterior region

Placing an implant between the mental foramina can cause nerve paralysis and subcutaneous bleeding from the floor of the mouth. In this study, we performed macroscopic anatomical measurements of the anterior loop of the mandibular canal and three-dimensional observations of the anterior loop, mandibular incisive canal, and lingual foramen using dental cone-beam computed tomography (CBCT) to understand the morphology of the anatomical structures between the mental foramina. The specimens comprised 13 donated bodies. After CBCT imaging, the cortical bone anterior to the mental foramen was removed to isolate the anterior loop. After taking a picture, the anterior loop was measured using the image data. Additionally, a three-dimensional reconstruction of the CBCT images was performed to observe the anatomical structures between the mental foramina. The vertical distance from the superior margin of the mental foramen to inferior border of the mandibular canal was 7.34 mm and that from the inferior border of the mandibular canal to inferior border of the mandible was 8.90 mm. The anteroposterior distance from the anterior margin of the mental foramen to the anterior border of the loop was 3.42 mm. No significant differences were found in any of the measurements between male and female. In segmented CBCT images of the interforaminal region, the mandibular incisive canal could be observed and the lingual foramen was also observed in the cortical bone. To prevent complications, paying close attention to the anterior loop, mandibular incisive canal, and lingual foramen when placing an implant between the mental foramina is necessary.