Computerized 3-dimensional study of the embryologic development of the human masticatory muscles and temporomandibular joint

Purpose: In this study, the development of human embryonic temporomandibula r joint (TMJ) and masticatory muscles were investigated by using computed 3 -dimensional reconstructions. Materials and Methods: Sixteen human embryos and fetuses, ranging from 6.5 to 107 mm crown-rump length, were examined. Results: At 10 weeks, a band of mesenchyme extending from the attachment of the lateral pterygoid muscle to the condylar process was observed to pass through the medial side of the condylar process to attach to the malleus. T he temporal, masseter, and pterygoid muscles develop from the so called "te mporal muscle" primordium, and the temporal muscle was in continuity with t he masseter muscle until 14 weeks of fetal life. Conclusions: The study shows that the muscles of mastication arise from a s ingle primordium. It also confirms the presence of a ligamentous attachment between the lateral pterygoid muscle and the malleus. (C) 2000 American As sociation of Oral and Maxillofacial Surgeons.