Measurement of Anterior Loop Length for the Mandibular Canal and Diameter of the Mandibular Incisive Canal to Avoid Nerve Damage When Installing Endosseous Implants in the Interforaminal Region

Purpose To measure the anterior loop length (ALL) for the mandibular canal and diameter of the mandibular incisive canal at various points to ascertain the mesial distance from the mental foramen at which it is safe to install endosseous implants in the most distal area of the interforaminal region. Patients and Methods Using 38 cadavers (75 hemimandibles), the ALL and the diameter of the incisive canal at its origin and at 1 mm intervals up to 5 mm mesially from the origin were measured using operative calipers. Results Measured data are expressed as minimum, maximum, and mean ± standard deviation. ALL was 0.0, 6.0, and 1.5 ± 1.4 mm, the diameter of the incisive canal was 1.0, 6.6, and 3.1 ± 1.2 mm at the origin, 0.6, 5.8, and 2.6 ± 1.1 mm at 1 mm, 0.5, 5.7, and 2.2 ± 1.0 mm at 2 mm, 0.5, 6.0, and 2.0 ± 1.0 mm at 3 mm, 0.5, 5.0, and 1.8 ± 0.8 mm at 4 mm, and 0.5, 4.9, and 1.7 ± 0.8 mm at 5 mm mesially. Conclusion The above results showed that because there may be large variations in the ALL and the diameter of the incisive canal, one should not assume that a fixed distance mesially from the mental foramen will be safe. Intraoperative examination of vital structures is indispensable for the safe installation of implants in the interforaminal area of the mandible. Not only the ALL but also the diameter of the incisive canal should be investigated on a case-by-case basis to determine the appropriate location for each individual.