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BIOMECHANICAL BEHAVIOR OF THE TEMPOROMANDIBULAR JOINT DISC
Eiji Tanaka1,* and
Theo van Eijden2
1 Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan; and
2 Department of Functional Anatomy, Academic Center for Dentistry Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands;

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Figure 1. Diagram showing the different types of strain for three directions of loading. During compressive loading, the disc becomes shorter in the loading direction; during tensile loading, it is stretched in the loading direction; and during shear loading, one boundary surface of the disc moves parallel to an adjacent surface.
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Figure 2. Typical stress-strain curve for connective tissue. The elastic and plastic regions of the curve are divided by the yield point, beyond which deformation causes tissue failure; the elastic region is further divided into a toe region and a transition zone.
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Figure 3. Stress-relaxation (A) and creep and restoration curves (B). In the hysteresis curve (C), the area enclosed by the stress-strain curve is a measure for the energy dissipation.
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Figure 4. Relaxation and creep function of (A) Maxwell, (B) Voigt, and (C) Kelvin model (standard linear solid). Maxwells model and Voigts model consist of only two elements, which are a linear spring with a spring constant µ and a dashpot with a coefficient of viscosity , whereas Kelvins model is composed of a combination of two springs and a dashpot. A linear spring produces an instantaneous deformation proportional to the stress. A dashpot produces a velocity proportional to the stress at any instant.
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Figure 5. Schematic representation of the relationship between stress and strain during a sinusoidal oscillating strain ( , angular velocity) for a perfectly elastic solid (A, Hookean body), a viscoelastic material (B), and a perfectly viscous liquid (C, Newtonian body). In a viscoelastic material, the phase difference between stress and strain is somewhere between ( /2 > > 0), and the complex modulus E* is resolved into two components, i.e., the storage modulus E' and the loss modulus E'', shown vectorially. Furthermore, the tangent of the phase angle ( ) between stress and strain is a measure of the ratio of energy loss to energy stored during a cyclic deformation.
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Figure 6. Schematic illustration of the disc (antero-lateral view) with various orientations of collagen fibers.
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Figure 7. Experimental stress-relaxation curve ( = strain level) under compression (A). Experimental stress-relaxation plots obtained from discs (mean ± 1 SD) with a theoretical curve calculated from the linear regression model with the time constants (B). Data from Tanaka et al. (1999).
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Figure 8. Experimental creep and restoration curve under tension (A). Experimental creep (B) and restoration (C) plots with theoretical curves. The graphs (B) and (C) are enlarged at the onset of the stress application and stress removal. Data from Tanaka et al. (2002a).
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Figure 9. Measurement signals of a cyclic test with a constant frequency. Data from Beek et al. (2001a). (A) Stress vs. time. (B) Strain vs. time. (C) Stress vs. strain.
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Critical Reviews in Oral Biology & Medicine, Vol. 14, No. 2,
138-150 (2003)
DOI: 10.1177/154411130301400207

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