Tensile biomechanical properties of human temporomandibular joint disc: Effects of direction, region and sex

Abstract

Approximately 30% of temporomandibular joint (TMJ) disorders include degenerative changes to the articular disc, with sex-specific differences in prevalence and severity. Limited tensile biomechanical properties of human TMJ discs have been reported. Stress relaxation tests were conducted on TMJ disc specimens harvested bilaterally from six males and six females (68.9 ± 7.9 years), with step-strain increments of 5%, 10%, 15%, 20% and 30%, at 1% strain-per-second. Stress versus strain plots were constructed, and Young’s Modulus, Instantaneous Modulus and Relaxed Modulus were determined. The effects of direction, region, and sex were examined. Regional effects were significant (p<0.01) for Young’s Modulus and Instantaneous Modulus. Anteroposteriorly, the central region was significantly stiffer than medial and lateral regions. Mediolaterally, the posterior region was significantly stiffer than central and anterior regions. In the central region, anteroposteriorly directed specimens were significantly stiffer compared to mediolateral specimens (p<0.04). TMJ disc stiffness, indicated by Young’s Modulus and Instantaneous Modulus, were higher in directions corresponding to high fiber alignment. Additionally, human TMJ discs were stiffer for females compared to males, with higher Young’s Modulus and Instantaneous Modulus, and female TMJ discs relaxed less. However, sex effects were not statistically significant. Using second-harmonic generation microscopy, regional collagen fiber organization was identified as a potentially significant factor in determining the biomechanical properties for any combination of direction and region. These findings establish structure-function relationships between collagen fiber direction and organization with biomechanical response to tensile loading, and may provide insights into the prevalence of TMJ disorders among women.

Estrogen signaling impacts temporomandibular joint and periodontal disease pathology

“…Cell populations in the disc are heterogeneous with 70% fibroblast-like fibrochondrocytes throughout the tissue and 30% chondrocyte-like fibrochondrocytes localized in the intermediate zone [40,41]. Biomechanical analysis of aged human TMJ discs illustrated an increase in overall stiffness and a reduction in relaxation after strain in female compared to male tissue [42]. Further, fixed charge density, the contribution of charged GAGs to the disc's ability to support load via osmotic pressure, was determined to be lower in aged female human discs compared to males [43].…”

Fixation Methods for Mandibular Advancement and Their Effects on Temporomandibular Joint: A Finite Element Analysis Study

“…Finally, we showed in our FEM that the highest stress levels at TMJ occurs on the posterior side, where also the highly innervated and vascularized intermediate region of retrodiscal tissue is [22]. These additional loadings might be in the tolerance range of biomechanical properties of the TMJ region [23]. We showed that fixation-related primary relapse of the mandibular segments does not correlate with the stress levels of TMJ.…”

Computational characterization of the porous‐fibrous behavior of the soft tissues in the temporomandibular joint

“…Figures show the different outcomes obtained for models defined with a single fiber orientation versus with multiple regions with distinct fiber orientations. Numerical tensile responses and Normalized Root Mean Squared Error (NRMSE) from data of Wright et al (), Singh and Detamore () and Murphy et al () are respectively shown in Figures . On the other hand, the results of the evaluation of the compressive response and its associated NRMSEs are shown in Figure .…”