Effect of jaw opening on the stress pattern in a normal human articular disc: finite element analysis based on MRI images

Abstract

IntroductionExcessive compressive and shear stresses are likely related to condylar resorption and disc perforation. Few studies have reported the disc displacement and deformation during jaw opening. The aim of this study was to analyze stress distribution in a normal articular disc during the jaw opening movement.MethodsBilateral MRI images were obtained from the temporomandibular joint of a healthy subject for the jaw opening displacement from 6 to 24 mm with 1 mm increments. The disc contour for the jaw opening at 6 mm was defined as the reference state, and was used to establish a two dimensional finite element model of the disc. The contours of the disc at other degrees of jaw opening were used as the displacement loading. Hyperelastic material models were applied to the anterior, intermediate and posterior parts of the disc. Stress and strain trajectories were calculated to characterize the stress/strain patterns in the disc.ResultsBoth the maximum and minimum principal stresses were negative in the intermediate zone, therefore, the intermediate zone withstood mainly compressive stress. On the contrary, the maximum and minimum principal stresses were most positive in the anterior and posterior zones, which meant that the anterior and posterior bands suffered higher tensile stresses. The different patterns of stress trajectories between the intermediate zone and the anterior and posterior bands might be attributed to the effect of fiber orientation. The compression of the intermediate zone and stretching of the anterior and posterior bands caused high shear deformation in the transition region, especially at the disc surfaces.ConclusionsThe stress and strain remained at a reasonable level during jaw opening, indicating that the disc experiences no injury during functional opening movements in a healthy temporomandibular joint.

Laser micro‐ablation of fibrocartilage tissue: Effects of tissue processing on porosity modification and mechanics

“…Samples were subject to unconfined compression under 20% deformation (strain) relative to original sample thickness for 15 cycles. This deformation was chosen based on MRI imaging and finite element modeling that shows change in disc thickness (compressive strain) at 15–20% while pathologic conditions such as bruxism can impart compressive strains up to 30% 31,32 . Deformation was defined as ε=ΔL/L 0 with ΔL the change in sample thickness relative to L 0 , the original samples thickness.…”

“…This deformation was chosen based on magnetic resonance imaging and finite element modeling that shows change in disk thickness (compressive strain) at 15-20% while pathologic conditions such as bruxism can impart compressive strains up to 30%. 31,32 Deformation was defined as E 5 DL/L 0 with DL the change in sample thickness relative to L 0 , the original samples thickness. An initial find contact of the platen at 0.05N was used to reset the displacement followed by a find contact of the sample at 0.05N.…”

Remaining Hurdles for Tissue-Engineering the Temporomandibular Joint Disc

“…The TMJ disc functions in a dynamic environment of compression, tension, and shear [63,64]. Finite element analysis shows stresses in the TMJ disc during mouth opening to be greater than 7 MPa in compression, 4 MPa in tension, and 1 MPa in shear [65]. For comparison, the hip experiences 7-10 MPa in compression and up to 18 MPa during stressful activities such as standing up [66,67].…”

Biomechanical behaviour of temporomandibular joints during opening and closing of the mouth: A 3D finite element analysis

“…Li et al conducted two-dimensional finite element (FE) analysis of the stress distributions during jaw opening. 16 Del Palomar and Doblaré simulated jaw opening and lateral excursions with a focus on the stress on discs and ligaments. [17][18][19] They demonstrated that the lateral part of the intermediate zone of the healthy joint sustained the highest stresses during jaw opening.…”

“…Almost the bone structures in all the FE models were considered as a rigid body due to the focus on the stress of the soft tissue. [16][17][18][19]21 However, some symptoms of TMD were associated with bony structures (eg, osteoarthritis). Thus, in this study, we simultaneously considered the maxillofacial system including TMJs as deformable and analysed discs, temporal bones, and condyles, as well as temporal and condylar cartilages.…”