Biomechanical tissue characterization of the superior joint space of the porcine temporomandibular joint

The objective of this study was to characterize the biomechanical properties of articular cartilage in the superior joint space of the porcine temporomadibular joint (TMJ). These properties and thickness of the disk and fossa cartilage were obtained from eight joints using creep indentation. Five sites per surface were tested to obtain the aggregate modulus, Poisson's ratio, permeability, creep, recovery percentage, and cartilage thickness. Histology was also performed to characterize the orientation of the collagen fibers and the proteoglycan content. It was found that the temporal fossa cartilage was 57% thinner and 50% stiffer than the disk. The aggregate modulus of the porcine TMJ disk and fossa was much smaller, but the permeability of the TMJ disk and fossa was much higher than those of articular cartilage in other joints. It was also noted that the TMJ disk did not fully recover following indentation testing unlike the articular cartilage in other joints. The biomechanical properties of the TMJ disk and temporal fossa obtained in this study are significantly different from those of cartilage present in other diarthrodial joints. This suggests that the function of the fibrocartilage in the superior TMJ space is substantially different from that of hyaline cartilage in other joints.