Prenatal development of the human mandible

Abstract

In an effort to better understand the interrelationship of the growth and development pattern of the mandible and condyle, a sequential growth pattern of human mandibles in 38 embryos and 111 fetuses were examined by serial histological sections and soft X-ray views. The basic growth pattern of the mandibular body and condyle appeared in week 7 of fertilization. Histologically, the embryonal mandible originated from primary intramembranous ossification in the fibrous mesenchymal tissue around the Meckel cartilage. From this initial ossification, the ramifying trabecular bones developed forward, backward and upward, to form the symphysis, mandibular body, and coronoid process, respectively. We named this initial ossification site of embryonal mandible as the mandibular primary growth center (MdPGC). During week 8 of fertilization, the trabecular bone of the mandibular body grew rapidly to form muscular attachments to the masseter, temporalis, and pterygoid muscles. The mandible was then rapidly separated from the Meckel cartilage and formed a condyle blastema at the posterior end of linear mandibular trabeculae. The condyle blastema, attached to the upper part of pterygoid muscle, grew backward and upward and concurrent endochondral ossification resulted in the formation of the condyle. From week 14 of fertilization, the growth of conical structure of condyle became apparent on histological and radiological examinations. The mandibular body showed a conspicuous radiating trabecular growth pattern centered at the MdPGC, located around the apical area of deciduous first molar. The condyle growth showed characteristic conical structure and abundant hematopoietic tissue in the marrow. The growth of the proximal end of condyle was also approximated to the MdPGC on radiograms. Taken together, we hypothesized that the MdPGC has an important morphogenetic affect for the development of the human mandible, providing a growth center for the trabecular bone of mandibular body and also indicating the initial growth of endochondral ossification of the condyle.

Mathematical Analysis of Mandibular Morphogenesis by Micro‐CT‐Based Mouse and Alizarin Red S‐Stained‐Based Human Studies During Development

“…The mandibular growth pattern is characterized by intramembranous ossification of the mandibular body and endochondral ossification of the condyle (Lee et al, 2001). The mammalian mandible is a complex morphological structure consisting of multiple morphogenetic components that form the final structure (Atchley, 1993).…”

Distribution of Tenascin-C and -X, and Soft X-ray Analysis of the Mandibular Symphysis during Mandible Formation in the Human Fetus

“…In our results, radiographic density level at the MS of the mandible gradually increased from 16 weeks to 28 weeks. Lee et al (2001) suggested that the genioglossus muscle was attached to the connective tissue of Meckel's cartilage in the early stage (12 weeks gestation) and masseter and suprahyoid muscles were not attached in this stage. However, tendon of muscle fiber in human hyoid muscles (digastric and geniohyoid muscles) was inserted into the periosteum and endosteum connective tissue of immature and mature bone at the medial region of the mandible at 28 weeks gestation.…”

“…The mandibular symphysis (MS) (Lee et al, 2001) undergoes a different ossification process to that of the mandibular body (Bareggi et al, 1994). In the formation of human mandible, the mental protuberance comes from fibrous cartilage in the syndesmosis and synostosis (Sperber, 2001).…”

“…In comparison with the MS, the cartilage assists in the formation of the mandibular body via endochondral ossification. Condensed cellular mesenchyme of the condylar blastema is closely associated with the perichondral fibrous tissue of Meckel's cartilage (Lee et al, 2001). The function and development of masticatory muscles affect the development of the human mandible (Bresin et al, 1999;Kiliaridis and Katsaros, 1998;Sato et al, 1994).…”

Amphibians as research models for regenerative medicine

“…Since amputated urodele limbs know how to do this, unraveling how they of the first pharyngeal arch at 5-6 weeks post-conception. 72,73 Ossification begins at each side of the mandible in the region of the bifurcation of the inferior alveolar nerve and artery into mental and incisive branches. The ossification spreads upwards, dorsally and ventrally to form a trough for the developing teeth, the body and the ramus of the mandibles, respectively.…”