Morphological variability of the human inferior alveolar nerve

The aims of this study were: to compare the radiographic appearance of the neurovascular bundle and its surrounding bone with the actual situation revealed on dissection; to reveal the morphology of the neurovascular bundle in dentate and edentulous subjects; and to note any changes occurring following the removal of the teeth and the consequent resorption of alveolar bone. Twenty-nine human mandibles were examined; 20 were dry skeletal specimens that were examined radiographically and the remaining nine were radiographed then dissected after decalcification and the branches of the inferior alveolar nerve were identified, sketched, and photographed. Different patterns of identifying characteristics of the mandibular canal were noted on the radiographs, ranging from alternating bands of radiopacity and radiolucency to continuous radiopaque lines. Dissections indicated that the radiographic appearance related to the number, distribution, and pattern of trabeculae around the canal. The dissections revealed that in all cases, the main nerve divided into its incisive and mental branches in the molar area well before reaching the mental foramen. A branch to the molar teeth, and in two instances to the second premolar as well, was given off from the main trunk before it divided into incisive and mental branches. In the dentate specimens, the neurovascular bundle formed two distinct curvatures, one between the mandibular and mental foraminae and the other between the mental foramen and the incisor teeth apices. In the edentulous specimens, the neurovascular bundle was reduced in size and although some small nerve branches, notably to the molar areas, were distinguishable, the blood vessels seemed to have atrophied beyond macroscopic identification. This project confirmed the inaccuracy of descriptions repeated in many anatomical textbooks suggesting that the inferior alveolar branch of the trigeminal nerve divides at the mental foramen into its incisive and mental branches and that during their path through the body of the mandible they give off fibers to the individual teeth. It further confirmed that the neurovascular bundle reduces in size quite markedly after removal of teeth and that the vascular component cannot be clearly identified.