Role of Interstitial Fluid Pressurization in TMJ Lubrication

Abstract

In temporomandibular joints (TMJs), the disc and condylar cartilage function as load-bearing, shock-absorbing, and frictionreducing materials. The ultrastructure of the TMJ disc and cartilage is different from that of hyaline cartilage in other diarthrodial joints, and little is known about their lubrication mechanisms. In this study, we performed micro-tribometry testing on the TMJ disc and condylar cartilage to obtain their region-and direction-dependent friction properties. Frictional tests with a migrating contact area were performed on 8 adult porcine TMJs at 5 different regions (anterior, posterior, central, medial, and lateral) in 2 orthogonal directions (anterior-posterior and medial-lateral). Some significant regional differences were detected, and the lateral-medial direction showed higher friction than the anterior-posterior direction on both tissues. The mean friction coefficient of condylar cartilage against steel was 0.027, but the disc, at 0.074, displayed a significantly higher friction coefficient. The 2 tissues also exhibited different frictional dependencies on sliding speed and normal loading force. Whereas the friction of condylar cartilage decreased with increased sliding speed and was independent of the magnitude of normal force, friction of the disc showed no dependence on sliding speed but decreased as normal force increased. Further analysis of the Péclet number and frictional coefficients suggested that condylar cartilage relies on interstitial fluid pressurization to a greater extent than the corresponding contact area of the TMJ disc.

Calcium signaling of in situ chondrocytes in articular cartilage under compressive loading: Roles of calcium sources and cell membrane ion channels

“…Compression of ECM can squeeze the interstitial fluid out of the cartilage, which in theory should generate fluid flow or shear stress on cell membrane. Due to the low permeability of ECM, fluid flow speed in the loaded cartilage is extremely slow and at tens of nanometers per second, 34,35 and the resulting fluid shear stress on cell membrane is negligible in comparison to those studies of fluid flow induced calcium signaling ($5-40 dynes/cm 2 ). Thus fluid flow might be a minor stimulation responsible for the [Ca 2þ ] i responses of in situ chondrocytes.…”

Jaw closing movement and sex differences in temporomandibular joint energy densities

“…24 Plus, the interstitial fluid pressurisation plays an important role in load carriage in articular cartilages. 14,25,26 The current study demonstrated that in both sexes, the distance of stress-field translation (ΔD) was significantly larger during jaw closing from laterotrusion than symmetric jaw closing and, thus, accounts for more mechanical work done per jaw closing cycle. Furthermore, the concentration of mechanical work per volume of cartilage was significantly larger in the healthy TMJs of females than males for both jaw closure from laterotrusion and symmetric jaw closing.…”

“…Stress‐field translation moves fluids through the disc, which, in turn, provides nutrition and waste disposal . Plus, the interstitial fluid pressurisation plays an important role in load carriage in articular cartilages . The current study demonstrated that in both sexes, the distance of stress‐field translation ( ΔD ) was significantly larger during jaw closing from laterotrusion than symmetric jaw closing and, thus, accounts for more mechanical work done per jaw closing cycle.…”

Biomechanical properties of murine TMJ articular disc and condyle cartilage via AFM-nanoindentation

“…This trend is reversed along the mediolateral orientation, where in the intermediate region, the relaxed modulus is 0.58 ± 0.39 MPa for the disc, and 3.6 ± 2.0 MPa for the condyle cartilage (Detamore and Athanasiou, 2003; Singh and Detamore, 2008). While these uniaxial test results do not show that the TMJ discs of larger animals have substantially lower resistance to indentation than the condyle cartilage, under spherical microindentation ( R ≈ 0.8 mm), porcine condyle cartilage is shown to have substantially higher aggregated modulus than the disc when tested at similar forces, with 36 ± 9 kPa for the disc and 250 ± 60 kPa for the condyle cartilage (mean ± std) (Lu et al, 2009; Zimmerman et al, 2015). These quantitative results thus suggest that the >5 × higher modulus observed on murine condyle cartilage (Fig.…”