Temporomandibular joint (TMJ) disorder affects over 10 million people in the US each year. Despite ongoing research, there is a current lack of understanding in the TMJ biomechanics field related to human biomechanical function. This has been attributed to the low success rate of replacement therapy as well as the inability to manage progressive pathology of the joint. As a result, significant advances in research are essential to understand the pathophysiology of joint degeneration for early diagnosis and management. It is generally believed that pathological mechanical loadings, e.g. sustained jaw clenching or malocclusion, trigger a cascade of molecular events leading to TMJ disc degeneration, which has been implicated in over 30% of TMJ disorders. Our previous studies indicate that the nutrient concentrations dictate TMJ cell metabolism and matrix synthesis. Due to the technical difficulty of measuring the in vivo mechanical and nutrient environment inside the TMJ, a finite element model must be developed to simulate the effect of mechanical loading on the nutrient diffusivities inside the TMJ disc. A deeper understanding of the biomechanics, i.e. mechanical environment and effect on the nutrient environment, could lead to developments in TMJ disorder diagnosis and management. Therefore, the objective of this research study is to develop an accurate mathematical model (finite element model) based on the first ever human characterization of the human mechanical and transport properties. Our central hypothesis is that sustained mechanical loading can alter solute transport and nutrient levels in the TMJ disc as well as mechanical function resulting in disc derangement and degeneration. We further hypothesize that by testing human TMJ discs with porcine TMJ discs under the same protocol, we will better understand the relevance of the porcine model to the human.
Aim 1 : Determine mechanical properties of human and porcine TMJ discs and correlate the mechanical properties to the tissue composition.
Aim 2 : Determine strain-dependant transport properties of human and porcine TMJ discs.
Aim 3 : Develop 3D patient specific multiphasic mechano-electrochemical finite element model of the human TMJ disc. The outcome of this study will yield 1) a patient specific finite element model to build a pathway between biomechanics and pathobiology 2) the first study to characterize the biomechanical properties of the human TMJ disc 3) the first study to establish the porcine biomechanical model in reference to the human for developments in tissue replacements and regenerative therapies. Finally, the project will bring the clinical field crucial, non-invasive method to screen and manage progression of patients with TMJ disorders.
The proposed study will characterize the mechanical/transport environment of the human and porcine TMJ disc and develop a novel 3D multiphasic patient specific finite element model. The outcome will establish complete human TMJ disc material property characterization and determine efficacy of the porcine mechanical model. Finally, through the development of the patient specific model, the clinical field will have a non-invasive diagnostic tool to analyze the effect of pathological mechanical loading on the TMJ disc nutrient environment in patients with TMJ disorder.
