IADR Abstract Archives
Determining TMJ Disc Nutrient Environment Under Load: A Bioengineering Approach
Objectives: The temporomandibular joint (TMJ) disc nutrient environment (e.g. glucose, lactate and oxygen concentrations) could affect cell energy metabolism, resulting in changes in cell proliferation, differentiation, and biosynthesis. Due to technical challenges of in vivo measurements, the extracellular nutrient environment inside the human TMJ disc remains unclear. Nutrient levels in the avascular TMJ disc depend on diffusion and consumption/production rates, as well as disc morphometry (i.e. size and shape) and mechanical loading. The objective of this study was to determine the 3D nutrient profiles in the TMJ disc under loading conditions using a bioengineering approach.
Methods: Glucose and lactate diffusivity (n=6 discs) were measured using a custom-built diffusion chamber, and glucose consumption/lactate production rates were measured during in vitro tissue culture (n=30 discs) under different oxygen and glucose conditions within a metabolic chamber. TMJ anatomy was obtained from magnetic resonance imaging and cone beam computed tomography (n=18 human subjects). With these inputs and our previous oxygen consumption rate data, subject-specific finite element models were developed to determine the 3D nutrient profiles in human TMJ discs with and without loading.
Results: Our results showed the physiological concentration ranges of glucose, lactate and oxygen inside the human TMJ disc were 0.2-4.0 mM, 0.9-2.3 mM and 0.001-5.8 kPa without loading. The “critical zone” volumes (glucose concentration<0.5 mM) in the anterior and posterior disc regions were 3.5±2.8% normalized by total disc volume without loading and increased to 10.13±3.71% with loading (p<0.0001).
Conclusions: Nutrient gradients inside the TMJ disc are steep and sensitive to loading, and could be vulnerable to pathological events which would impede nutrient supply, including abnormal anatomical structure or sustained joint loading (e.g. clenching and bruxism). This study provides new insights into the TMJ disc nutrient environment, and could provide a potential mechanism of TMJ disc degeneration.
Methods: Glucose and lactate diffusivity (n=6 discs) were measured using a custom-built diffusion chamber, and glucose consumption/lactate production rates were measured during in vitro tissue culture (n=30 discs) under different oxygen and glucose conditions within a metabolic chamber. TMJ anatomy was obtained from magnetic resonance imaging and cone beam computed tomography (n=18 human subjects). With these inputs and our previous oxygen consumption rate data, subject-specific finite element models were developed to determine the 3D nutrient profiles in human TMJ discs with and without loading.
Results: Our results showed the physiological concentration ranges of glucose, lactate and oxygen inside the human TMJ disc were 0.2-4.0 mM, 0.9-2.3 mM and 0.001-5.8 kPa without loading. The “critical zone” volumes (glucose concentration<0.5 mM) in the anterior and posterior disc regions were 3.5±2.8% normalized by total disc volume without loading and increased to 10.13±3.71% with loading (p<0.0001).
Conclusions: Nutrient gradients inside the TMJ disc are steep and sensitive to loading, and could be vulnerable to pathological events which would impede nutrient supply, including abnormal anatomical structure or sustained joint loading (e.g. clenching and bruxism). This study provides new insights into the TMJ disc nutrient environment, and could provide a potential mechanism of TMJ disc degeneration.