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Effects of introducing gap constraints in the masticatory system: A finite element study
Published in J. Belinha, R.M. Natal Jorge, J.C. Reis Campos, Mário A.P. Vaz, João Manuel, R.S. Tavares, Biodental Engineering V, 2019
S.E. Martinez Choy, J. Lenz, K. Schweizerhof, H.J. Schindler
The temporomandibular joint (TMJ) is a synovial joint which articulates the jaw to the skull. It is composed principally by the mandibular condyle, the mandibular fossa, the articular disc, the capsule, the ligaments and the lateral pterygoid muscle. The articulating surfaces of the condyles and the mandibular fossa are covered with articular cartilage, which together with the synovial fluid allows for a very low coefficient of friction and a uniform transmission of compressive forces to the bone (Radin et al. 1971). The articular cartilage of the TMJ contains both collagen fibers type I and type II, which classifies it as fibrocartilage. Due to the low permeability of the tissue, compression forces rapidly increase fluid pressure, which in turn carries the major part of the load through hydrostatic pressurization (Mow et al. 2005). The collagen fibers of the cartilage, on the other hand, resist the stretching of the tissue from tensile forces (Hukins et al. 1984). The articular disc, also composed of fibrocartilage, lies between the mandibular condyle and the fossa, dividing the synovial joint in two. It distributes loads and dissipates the energy caused from impact loads. The disc allows for relative motion between the condyle and the temporal bone. In the case of the condyle, both translational and rotational motions are possible. The articular disc is connected to the articular surfaces through the joint capsule. The attachments of the joint capsule can be divided as shown in Figures 1–2 into medial, lateral, anterior and posterior attachments. These attachments give the disc a range of movement and at the same time avoid extreme displacements that may result in the dislocation of the disc.
Optimization and Dose Reduction in Dentomaxillofacial Imaging
Published in Lawrence T. Dauer, Bae P. Chu, Pat B. Zanzonico, Dose, Benefit, and Risk in Medical Imaging, 2018
Bone lesions of the gnathic structures and temporomandibular joint (TMJ) disorders, more often than not, present with pain and/or swelling. Malignant lesions involving the gnathic bones are often accompanied by paresthesia. The imaging component of the diagnosis of such a lesion almost always begins with a panoramic image (Figure 5.11). This may be sufficient, but is often followed by advanced imaging, with CBCT being superior for bone lesions due to its extremely high spatial resolution. Where soft-tissue involvement is suspected, MDCT and/or MRI become the imaging of choice. CBCT is especially effective in defining the extent of intraosseous lesions and bone involvement by extraosseous lesions as well as mass effect and effects of lesions on teeth. All of these features are important in the final diagnosis of the problem. CBCT is the imaging of choice for defining the extent and severity of medication-related osteonecrosis of the jaws in patients receiving anti-bone-resorptive pharmacotherapy as part of treatment for malignant lesions, most often multiple myeloma and breast and prostate carcinomas. Osteoarthritic changes are frequently encountered in the TMJs. Evaluating TMJ area pain for osseous pathology is the realm of CBCT, which provides excellent detail of the configurations and osseous fine structures, enabling identification of the presence and severity of these changes (Figure 5.12). Even normal findings in the TMJ osseous components is diagnostically helpful as it can lead to further evaluation of the TMJ soft-tissue components, namely, of the articular disc and its osseous attachments as well as the presence or absence of inflammatory effusions within the joint spaces using MRI.
Musculoskeletal system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The radiocarpal joint is a synovial ellipsoid joint formed between the lower end of the radius and an articular disc together with the scaphoid lunate and triquetral. The joint capsule, which is separate from the distal radio-ulnar joint, encloses the joint and is reinforced by palmar radiocarpal, palmar ulnar-carpal, dorsal radiocarpal, ulna and radial collateral ligaments.
Three-dimensional morphological and biomechanical analysis of temporomandibular joint in mandibular and bi-maxillary osteotomies
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Bingmei Shao, Annan Li, Jingheng Shu, Hedi Ma, Shiming Dong, Zhan Liu
The HCA, MJS, and LJS showed significant preoperative and postoperative differences in both osteotomies (Figure 2). The average HCAs were approximately 52% greater than those of the control group in both the mono-pre and bi-pre groups. The significant differences did not disappear after the surgeries, and the magnitudes increased slightly for several individuals. The magnitudes of the MJS and LJS showed limited changes after the two surgeries, i.e. only approximately 70% of those from the control group. The low joint spaces (between the condyle and temporal bone) indicated that the condyle was in an abnormal position and caused disc compression. Although the joint space was released slightly after the surgery, possible asymmetry can be inferred from the abnormal space (Figure 2). The bone might be damaged without relief from loading. The articular disc is a type of fibrous cartilage that is used to cushion the condyle and articular fossa eminence. Additionally, the relationship between the stress and TMD based on the change in the joint spaces can be evaluated using the contact stresses. The finite element analysis showed that the contact stresses between the discs and articular surfaces of the left and right TMJs remained significantly different after the two operations (Figure 2(a,b)). Improper condylar positioning and axial changes caused TMD (Timmis, Aragon, and Van Sickels 1986; Luhr 1989; Westesson et al. 1991; Ueki et al. 2012). Additionally, TMD symptoms are typically present in the asymmetric faces (Ueki et al. 2012; Goncalves et al. 2013). The incidence of internal derangement of the TMJ in patients with facial asymmetry is higher than that in symmetrical patients (Ueki et al. 2012). In summary, the orthognathic surgeries could not completely improve the TMJ morphology but triggered significant differences postoperatively. It was discovered that the improvement in the maxillofacial deformities adversely affected some of the morphological parameters.