title: Roles of the Fibrous Superficial Zone in the Mechanical Behavior of TMJ Condylar Cartilage.
abstract: In temporomandibular joints (TMJs), the cartilage on the condylar head displays a unique ultrastructure with a dense layer of type I collagen in the superficial zone, different from hyaline cartilage in other joints. This study aims to elucidate the roles of this fibrous zone in the mechanical behaviors, particularly lubrication, of TMJ under physiological loading regimes. Mechanical tests on porcine condylar cartilage demonstrated that the superficial and middle-deep zones exhibit tension-compression nonlinearity. The tensile and compressive moduli of the superficial zone are 30.73 ± 12.97 and 0.028 ± 0.016 MPa, respectively, while those for the middle-deep zone are 2.43 ± 1.75 and 0.14 ± 0.09 MPa. A nonlinear finite element model of condylar cartilage was built to simulate sliding of a spherical probe over the articular surface. The presence of the superficial zone significantly promoted interstitial fluid pressurization (IFP) inside the loaded cartilage and reduced the friction force on the surface, compared to the case without the superficial zone. Finite element simulations showed that IFP depends on sliding speed but not normal load, which matches the experimental results. This study revealed the presence of the fibrous zone can significantly reduce the deformation of condylar cartilage under compression and the friction force on its surface during sliding.
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.|Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Ruggiero
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.
authors.forename: Brandon K
authors.initials: BK
authors.lastname: Zimmerman
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.
authors.forename: Miri
authors.initials: M
authors.lastname: Park
authors.affiliation: School of Biomedical Engineering, Science & Health Systems, Drexel University, Philadelphia, PA, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Han
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.
authors.forename: Liyun
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Burris
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA. xlu@udel.edu.
authors.forename: X Lucas
authors.initials: XL
authors.lastname: Lu
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000502:physiology*; D024042:Collagen Type I; D019245:Compressive Strength; D005260:Female; D017276:Friction; D008297:Male; D013314:Stress, Mechanical; D013552:Swine; D013704:Temporomandibular Joint / Q000502:physiology*; D013718:Tensile Strength
chemical_list: D024042:Collagen Type I
keywords: Biphasic theory; Finite element model; Friction coefficient; Heterogeneous; Interstitial fluid pressurization; Tension–compression nonlinearity