An Architectural Study on Lamellar Structures and the Fibrous Matrix of the Mandible

The masticatory pressure through the periodontal ligament and the tensile strength of the masticatory muscles function to the mandible as the composite stress.<BR>Using the mandible with all teeth removed from a man's body for anatomical laboratory, I examined the arrangement of the fibrous matrix constructing the bone lamellae of compact bone and bone trabeculae of spongy bone on the angle of mandible, the part of the mental foramen and the central part of the mandibular body, in which the composite stress particularly functioned, with a high-resolution scanning electron microscope. I then discussed the relationship between the stress to the bone and the arrangement of fibrous matrix and bone trabeculae.<BR>The inner and outer layers of the angle of mandible, at which the masseter muscle and the medial pterygoid muscle are attached, were constructed by matrix fibril bundles running from infero-anterior to supero-posterior. The Haversian lamellae of compact bone of the angle of mandible were constructed by the osteons, which ran diagonally from infero-anterior to supero-posterior. The inside of the angle of mandible was constructed by bone trabeculae of spongy bone, which was arranged from infero-anterior to supero-posterior, but at the central part, that is, the part of the mandibular foramen and mandibular canal, the bone trabeculae were not examined. At the upper part of the angle of mandible, bone trabeculae were comparatively sparse, and the bone marrow space expanded slightly. The upper and lower parts of the mental foramen of the mandibular body were constructed by matrix fibril bundles running from antero-superior to postero-inferior, and the upper part was constructed by matrix fibril bundles crossing each other and running from inferior to superior. On the other hand, the Haversian lamellae were constructed by bending osteons running around the mental foramen. At the alveolar part of the second premolar of the lower jaw, that is, the part of the mental foramen, the alveolar bone proper attached to the inner and outer boards of the supporting alveolar bone, but the spongy bone around the mental foramen was constructed by the comparative sparse bone trabeculae. The upper half of the mental part on the outside layer of mandibular body was constructed by matrix fibril bundles running from supero-anterior to infero-posterior, and matrix fibril bundles crossed on the central line. The matrix fibril bundles on the mental protuberance were arranged from superior to inferior. The Haversian lamellae of compact bone on the mental part were constructed by the bending osteons running horizontally. At the alveolar part of the central incisor of the lower jaw near the mental part, the alveolar bone proper was attached to the whole inner and outer boards of the supporting alveolar bone. The mental part was mainly constructed by the bone trabeculae running to infero-posterior.