Ultrastructural Study on Matrix Fiber Arrangement in the Young Adult Mandible

Abstract

The mandible took the tensile of muscle and the masticatory pressure. So it has been thought that the bone lamellae forming the adult mandible have the arrangement suitable for the tensile of the masticatory muscle and the masticatory pressure. On the purpose to study the relationship between collagen fibrils forming the bone lamellae of the compact bone in mandible and the stress on the mandible, I examined the arrangement of matrix fibrils of mandibles with all teeth dissected from young adult men's bodies for the anatomical laboratory.
The surface of the external basic lamellae in young adult mandible was formed by matrix fibril bundles of collagen fibrils in all areas. Matrix fibril bundles arranged suitable for the stress on the each part of mandible. At the alveolar crest, dense matrix fibril bundles ran backward. At the alveolar part, matrix fibril bundles ran downward or diagonal backward. Both matrix fibril bundles of the alveolar crest and the alveolar part transferred each other. At the mandibular body and the base of mandible, matrix fibril bundles ran in parallel to the under edge of the mandible. At the internal surface of the mandibular body, matrix fibril bundles on the surface over the mylohyoid line ran diagonal backward, and these bundles transferred to the fibril bundles running backward on the mylohyoid line. At the surface of Tuberositas masseterica, many tendons of masseter muscle entered between matrix fibril bundles.
In the external basic lamella, the surface layer was formed by the lamella of about 2.5μm thick composed of matrix fibril bundles which ran backward. The adjacent lamella was about 1μm thick, and matrix fibril bundles ran downward. Lamellae composed of matrix fibril bundles which ran in different direction piled up alternately.
In osteons forming the Haversian lamellae, the lamellae of about 4μm thick and about 1μm thick arranged alternately. Matrix fibril bundles in the lamellae of about 4μm thick ran along the long axis of the bone, and the bundles in the lamellae of about 1μm thick ran concentrically. In the each lamella of osteon, matrix fibril bundles ran parallel, and matrix fibril bundles crossed diagonally between adjacent lamellae.