Fracture toughness estimation for the TMJ disc

Area of Science:

• Biomechanics
• Biomaterials Science
• Orthodontics

Background:

• The temporomandibular joint (TMJ) disc is crucial for jaw function.
• Understanding TMJ disc mechanical properties, particularly fracture toughness, is vital for diagnosing and treating disc pathologies.
• Previous studies have not fully elucidated the anisotropic nature of TMJ disc fracture toughness.

Purpose of the Study:

• To estimate the J-contour integral fracture toughness of the temporomandibular (TMJ) disc using a computational model.
• To investigate the influence of crack orientation relative to collagen fibers on TMJ disc fracture toughness.
• To identify key variables affecting TMJ disc fracture toughness.

Main Methods:

• A computational model was developed based on experimental fracture load data.
• Stress analysis was performed on TMJ disc specimens with cracks oriented parallel and perpendicular to the collagen fiber axis.
• An orthotropic material model was employed to account for material anisotropy.

Main Results:

• Fracture toughness was significantly lower for cracks oriented parallel to the collagen fiber direction compared to perpendicular orientations.
• The orthotropic model revealed distinct differences in fracture toughness based on crack orientation.
• Disc thickness, crack size, and anisotropy ratio were identified as additional factors influencing fracture toughness.

Conclusions:

• Collagen fiber orientation plays a critical role in the fracture toughness of the TMJ disc.
• The anisotropic nature of the TMJ disc must be considered in biomechanical models.
• Future research should incorporate the poroviscoelastic properties of the TMJ disc for enhanced model accuracy.