Temporomandibular Joint Model for Asymptomatic and Dysfunctional Joints - Computational Biomechanics of the Musculoskeletal System - page 292

unilateral occlusion. If pain is present on one side of the TMJ, the pain will worsen if the contralat-
eral side is used for chewing.

22.4 bIomeChanICal modelS oF tyPICal temPoromandIbular

dISorderS

22.4.1 m odel d eVelopment
The base model of the dentate mandible was developed in MIMICS 8.1 (Materialise, Leuven,
Belgium) according to CT images of a person with normal occlusion and without TMD, as shown
in Figure 22.6. Likewise, the bilateral articular fossa-eminence complexes were also constructed.
The geometries of the cortical bones, cancellous bones, and the teeth were imported into ANSYS
8.0 (Swanson Analysis System Co., Houston, TX). The models of the fibrocartilage layers and the
articular discs were also constructed using the method detailed in Section 22.2.1. The minimum
thickness of the intermediate zone was about 1 mm, while the maximum thickness of the anterior
and posterior bands was 2 and 3 mm, respectively (Liu et al. 2007). The attachments of the articular
disc and the mandibular ligaments were also considered nonlinear cable elements, as described in
Section 22.2.2.
Seven models of typical TMDs were established based on the base model with normal TMJs:
relaxation of discal attachment (relaxation of anterior and posterior attachments), disc displace-
ment (anterior, posterior, medial, and lateral disc displacement), and disc perforation. Only the right
TMJs in the models were modified and the left joints were treated as healthy joints. Relaxation of
anterior and posterior attachments was simulated by decreasing the stiffness of the cable elements.
According to the typical morphology of the displaced discs, four models of disc displacement were
developed. Moreover, the bilaminar zones were not modeled in the anterior disc displacement with-
out reduction. Likewise, the temporal anterior attachment and mandibular anterior attachment were
not modeled in the posterior disc displacement; the inner layer of the temporomandibular ligament
was not considered in the medial disc displacement. Disc perforation typically occurs at the lateral
intermediate zone, so this region was perforated in the model of disc perforation.
The mechanical properties of the cortical bone, cancellous bone, articular cartilage, teeth, and
disc were identical to those described in Sections 22.2 and 22.3. The interfaces between the disc
and the articular surfaces of the condyle and the temporal bone were treated as contact elements, as
described in Section 22.2. Loading and boundary conditions of the centric occlusion were applied
to the models as described in Section 22.2.

FIgure 22.6 The model of the dentate madible.