At 8 weeks’ gestation, most other joint cavities are present in their initial form; but the TMJ develops later, and at this time there are only the embryologic condensations of the condyle, temporal bone, and articular disc that are visible without a defined framework.
These structures are derivatives of the first pharyngeal arch. The pharyngeal arches are paired structures that are embryologic derivatives for the pharynx and surrounding structures. They consist of a central somatic mesoderm and neural crest mesenchyme. The somatic mesoderm contributes to muscles and arteries. The neural crest mesenchyme typically forms bony or cartilaginous structures.
There are 3 stages that define the normal embryologic development of the TMJ: (1) blastemic, (2) cavitation, and (3) maturation stages.
The inferior joint space begins to develop first at 9 weeks. The superior joint space begins to develop at 11 weeks. The condyle forms a secondary cartilage due to endochondral bone formation that is covered with flat fibrous cells at 9 weeks. The development of glenoid fossa and condyle during this stage is influenced by surrounding vascular ingrowth and the muscle pressure forces. These factors influence the framework for the final morphology of the TMJ. At birth, the TMJ is relatively underdeveloped in comparison with other synovial joints.
Congenital deformities of the temporomandibular joint (TMJ) complex present as a heterogeneous continuum of growth disturbances of the mandibular condyle, articular eminence, and temporal bone. Such disturbances may occur in utero, specifically late in the first trimester. Any disruption in condylar development has an effect on TMJ morphology, which can result in a degree of aplasia or hypoplasia of the condyle. (Galea et al, 2018)
Pathological conditions taken into account are subdivided into (1) congenital malformations with associated growth disorders, (2) primary growth disorders, and (3) acquired diseases or trauma with associated growth disorders. Among the congenital malformations, hemifacial microsomia (HFM) appears to be the principal syndrome entailing severe growth disturbances. (Pirttiniemi et al, 2009)
Growth disturbances in the development of the mandibular condyle may occur in utero late in the first trimester and may result in disorders such as aplasia or hypoplasia of the mandibular condyle. Meanwhile, hyperplasia of the mandibular condyle is not visible at birth and seems to be gradually acquired during growth. (Kaneyama et al, 2008)
Acquired temporomandibular joint (TMJ)/condylar abnormalities, such as juvenile idiopathic arthritis, idiopathic condylar resorption, TMJ ankylosis, and condylar hyperplasia, often result in facial deformity and functional deficits. (Chouinard et al, 2017)
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Galea CJ, Dashow JE, Woerner JE. Congenital Abnormalities of the Temporomandibular Joint. Oral Maxillofac Surg Clin North Am. 2018 Feb;30(1):71-82. doi: 10.1016/j.coms.2017.09.003. PMID: 29153239.
Pirttiniemi P, Peltomäki T, Müller L, Luder HU. Abnormal mandibular growth and the condylar cartilage. Eur J Orthod. 2009 Feb;31(1):1-11. doi: 10.1093/ejo/cjn117. PMID: 19164410.
Kaneyama K, Segami N, Hatta T. Congenital deformities and developmental abnormalities of the mandibular condyle in the temporomandibular joint. Congenit Anom (Kyoto). 2008 Sep;48(3):118-25. doi: 10.1111/j.1741-4520.2008.00191.x. PMID: 18778456.
Chouinard AF, Kaban LB, Peacock ZS. Acquired Abnormalities of the Temporomandibular Joint. Oral Maxillofac Surg Clin North Am. 2018 Feb;30(1):83-96. doi: 10.1016/j.coms.2017.08.005. PMID: 29153240.