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The Anatomy of Joints Related to Function
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The menisci of the knee are perforated rings, but in other situations intraarticular disks may separate the joint cavity completely into two compartments. In these circumstances, different movements are facilitated on opposite sides of the disk. This is the case in the temporomandibular joint (Fig. 3B), where the intraarticular disk is complete and is attached to the circumference of the joint capsule. It conforms to the mandibular fossa on the temporal bone and can slide forward out of this depression, carrying the mandibular condyle with it. The disk has a direct connection to the posterior margin of the fossa, but this does not prohibit its anterior displacement because this attachment is significantly composed of elastic fibers; elsewhere, the capsule between disk and temporal bone is lax (52). Beneath the disk, movement between it and the mandibular condyle is constrained to rotation about a transverse axis by stout attachments directly to medial and lateral poles of the condyle. These attachments are analogous to the collateral ligaments of a hinge-type joint; anteriorly and posteriorly the “subdiskal” capsule is lax and permits the necessary movement (52).
Salivary Gland Anatomy
Published in John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford, Head & Neck Surgery Plastic Surgery, 2018
The lateral surface lies adjacent to the body of the mandible in the mandibular fossa and the origin of the medial pterygoid. The facial artery enters or deeply grooves the gland posteriorly, after emerging from deep to the superior margin of the posterior belly of the digastric. It initially lies deep to the gland before turning anterolaterally to emerge between the gland and the lower border of the mandible.
Evolution of Form in the Craniofacial Complex
Published in D. Dixon Andrew, A.N. Hoyte David, Ronning Olli, Fundamentals of Craniofacial Growth, 2017
The neurocranium in Homo erectus is elongated along its anterior-posterior axis, with marked expansion in the occipital region. Nuchal lines, but no real crests are present along the posterior inferior border of the occiput, approximately equidistant between lambda and the foramen magnum. Temporal lines rise up the lateral walls of the vault, sometimes ascending about two-thirds of the height of the parietais. Ovoid, convex mastoid processes begin their protrusion from the cortical surface of the outer table at or near the Frankfort plane. While possessing distinct supraorbital ridges that are separated from the cranial vault by a sulcus, a portion of the orbits are covered by the anterior cranial fossa. The zygomata are unremarkable in size, and their malar surfaces are directed laterally more so than anteriorly. The take-off for the zygomatic root is between the first and second molars, and there is a distinct fossa anteromedial to this area. The premaxilla is procumbent, but with a vertically oriented dentition. In contrast to earlier hominid forms, the maxillary components and the adjacent nasal bones that form the lateral and superior margins of the nasal aperture project outward from the facial plane, giving the nasal region a protrusive appearance and contributing to a convex facial profile. Compared with australopithecines, midfacial height in H. erectus is truncated, along with the vertical length of the mandibular ramus. The mandible is less robust overall, and still lacks a mental eminence. The anatomy of the mandibular fossae is very human-like. Each fossa is bounded anteriorly by a slight articular eminence, posteriorly by a deep glenoid fossa, and medially by an entoglenoid process. A post-glenoid process separates the mandibular fossa from the bony opening of the external auditory meatus.
Analysis of temporomandibular joint dysfunction in paediatric patients with unilateral crossbite using automatically generated finite element models
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Javier Ortún-Terrazas, José Cegoñino, Edson Illipronti-Filho, Amaya Pérez del Palomar
The temporomandibular joint (TMJ) is a complex mandibular articulator composed primarily of the TMJ disc, hyaline cartilages, and the disc attachments. The TMJ mainly develops during paediatric growth in response to the mechanical stimuli produced during chewing by the elevator (masseter, temporalis, medial pterygoid, and superior portion of the lateral pterygoid) and depressor (digastric, geniohyoid, mylohyoid, and the inferior portion of the lateral pterygoid) muscles (Bakke 2006; Chan et al. 2008). Healthy bilateral chewing occurs in an alternating manner: while one condyle compresses the TMJ disc with the mandibular fossa (working movement), the other moves the articular eminence forward (balancing movement) (Palla et al. 2003). While well-balanced chewing ensures proper development of both TMJs, unilateral crossbite (UXB) may result in morphological deformities in the TMJs.
Occlusal load modelling significantly impacts the predicted tooth stress response during biting: a simulation study
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Harnoor Saini, David C. Ackland, Lulu Gong, Oliver Röhrle
To this end, dental structures, including the first right mandibular molar enamel and dentin, the cortical and cancellous mandibular bone, and a section of the left and right mandibular fossa, were manually segmented from the CT scans using ITK-SNAP (version 2.4.0) (Yushkevich et al. 2006). Since dentin and cementum have similar mechanical properties (Shaw et al. 2004), these materials were combined into one structure. The thickness of the articular discs of the TMJ was defined from the width of the space between the mandibular condyles and the fossae. The periodontal ligament (PDL) geometry was based on the mandibular molar root geometry and defined as a uniform layer with an approximate thickness of 0.20 mm similar to other investigations (e.g. McGuinness et al. 1992; Toms and Eberhardt 2003). The maxillary first molar geometry was segmented from the micro-CT images. The rubber sample used in the biting simulations had dimensions 20x10x5mm (Röhrle et al. 2018).
Prevalence of sagittal molar and canine relationships, asymmetries and midline shift in relation to temporomandibular disorders (TMD) in a Finnish adult population
Published in Acta Odontologica Scandinavica, 2022
Elisa Tervahauta, Linnea Närhi, Pertti Pirttiniemi, Kirsi Sipilä, Ritva Näpänkangas, Mimmi Tolvanen, Ville Vuollo, Anna-Sofia Silvola
The results of this study showed that half-cusp Class II and Class II seem to be more frequent in adults with TMD than Class III. Sagittal malocclusions have previously been found to relate to TMJ changes, especially in Class II vertical cases [35], and in Class II and Class III discrepancies [36]. Paunonen et al. [37] reported that Class II malocclusion and retrognathic mandible were associated with pain-related TMD diagnoses. It has also been found that Class II malocclusion is associated with the altered position of the condyle in the mandibular fossa [38]. Furthermore, the distal position of the mandible may expose especially to disc displacement [35].