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Static and Dynamic Loading Effects on Temporomandibular Joint Disc Tractional Forces

¹ University of Nebraska Medical Center College of Dentistry, Departments of Growth and Development,
² Oral Biology, and
³ Adult Restorative Dentistry, PO Box 683740, Lincoln, NE 68583-0755, USA;
⁴ private practice, 1817 17th St., Cody, WY 82414, USA; and
⁵ University of Nebraska, Department of Statistics, 340 Hardin Hall North, Lincoln, NE 68583-0963, USA

View larger version (12K): [in this window] [in a new window]   Figure 1. Effects of duration of static loading of the TMJ disc on compressive strain (left vertical axis) and tractional coefficient at start of movement (right vertical axis). Average compressive strain was significantly larger (***p < 0.0001) following 30 sec (n = 32, SE = ± 0.012) of static loading than following 1 sec (n = 32, SE = ± 0.012 ) of static loading. Similarly, average tractional coefficients at the start of movement were significantly larger (a, b; p < 0.0001) following 30 sec (n = 32; SE = ± 0.032) than after 1 sec (n = 32, SE = ± 0.032) of static loading. Vertical bars indicate standard errors of the means. Measurements were made during the 0.003 sec following the start of movement. Velocities of movement during this time were less than 10 mm/sec.

View larger version (18K): [in this window] [in a new window]   Figure 2. Compressive strain effects on tractional coefficient at the start of movement. Compressive strains of the TMJ discs ranged between less than 5% to greater than 40% of original thickness following 1 sec (n = 32) and 30 sec (n = 32) of static loading. Measurements were made during the 0.003 sec following the start of movement. Velocities of movement during this time were less than 10 mm/sec.

View larger version (20K): [in this window] [in a new window]   Figure 3. Effects of cycle number and static loading duration on peak tractional coefficient. Results from two-way ANOVA. The error bar is the standard error of the mean. Data are presented for 1 sec (blank bars) and 30 sec (hatched bars) of static loading prior to pendulum movement (n = 32). The brackets compare 1 sec vs. 30 sec of static loading for a given cycle number. *** = significant differences at the p 0.01 confidence level; n.s. = non-significant differences (p 0.01). Letters denote comparisons of peak tractional coefficients for different cycles. Lower-case letters compare tractional coefficients for 1 sec of static loading vs. the cycle number, and upper-case letters compare tractional coefficients for 30 sec of static loading vs. cycle number. Groups with the same letters represent non-significant differences (p 0.01), and groups with different letters represent significant differences at a p 0.01 confidence level.

View larger version (27K): [in this window] [in a new window]   Figure 4. Relationship between normalized instantaneous tractional coefficient (instantaneous µT/peak µT) and velocity of stress-field translation during Cycles 2 and 3. Criteria for inclusion of the data were synchronization of peak tractional force with peak velocity during Cycles 2 and 3, and smooth transition of the tractional force as the velocity of translation decreased to zero and then accelerated to peak velocity in the opposite direction (n = 14 discs). Velocity of stress-field translation varied between +80 and -80 mm/sec. Positive velocities indicate movement of the stress-field toward pressure transducer #9, whereas negative velocities indicate movement toward pressure transducer #1.

Journal of Dental Research, Vol. 85, No. 9, 809-813 (2006)
DOI: 10.1177/154405910608500906


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