Reflex Jaw Motions and Jaw Stiffness Pertaining to Whiplash Injury of the Neck

Christensen, Larry; McKay, Duane C.

doi:10.1080/08869634.1997.11746018

Cited by 9 publications

(33 citation statements)

References 24 publications

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“…For the entire subject material (n= 4), an arithmetic grand mean (x ) represented the electrokinesiography of all subjects; a coefficient of variation (CV) represented the dispersion of x, where CV =standard deviation (SD) of x divided by x. For illustrations of electrokinesiographic displacement/velocity diagrams, see Christensen & McKay (1997).…”

Section: Instrumentationmentioning

confidence: 99%

“…For the myoelectrical observations, the model EMG-4 electromyograph* was used. Although the system records both the amplitude (mV) and the duration (ms) of surface myoelectrical activity, only the duration variable in synchrony with electrokinesiography was applied in this study (Christensen & McKay, 1997;McKay & Christensen, 1999). Bipolar silver/silver-chloride surface electrodes (interelectrode distance of 20 mm; impedance of 200 V at 60 Hz) were affixed over the right and left anterior temporalis muscles, the right and left anterior suprahyoid muscles (platysma, digastric, mylohyoid, geniohyoid muscles), and the right and left sternocleidomastoid muscles (level of the gonial angle of the mandible).…”

Section: Instrumentationmentioning

confidence: 99%

“…As a standard expression of the mass of a human mandible and appended tissues, the value of 0·2754 kg was used (Christensen & McKay, 1997). By inserting the latter mass value into Newton's second law of kinetics, we derived biologic estimates of the kinetic net forces generating accelerations ( + g n ) and decelerations ( − g n ) of the mandible.…”

Section: Kinematics/kineticsmentioning

confidence: 99%

“…Because the observed mandibular depressions/elevations approximated sinusoidal motions, it seemed reasonable to use k = kg mm − 1 as an expression of the elasticity (stiffness) of the mandibular locomotor system. In this case, k = kg mm − 1 is an approximation representing the elasticity of the passive (absence of motor innervation) and active (presence of motor innervation) contractile elements of the mandibular locomotor system (Lynn & Yemm, 1971;Yemm & Nordstrom, 1974;Akazawa, Milner & Stein, 1983;Christensen & McKay, 1997). Furthermore, if an elastic constant for mandibular elevation is divided by that for mandibular depression, we obtain an elevator elastic efficiency factor above or below zero, depending on the magnitudes of the two elastic constants.…”

Section: Kinematics/kineticsmentioning

confidence: 99%

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Kinematic and kinetic observations on ballistic depression and elevation of the human mandible

Christensen¹,

McKay²

2000

J of Oral Rehabilitation

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To study mandibular motions with respect to time (kinematics) and the forces causing and resulting from these motions (kinetics), four subjects generated rapid depression and elevation of the mandible (displacement of 0.224 m; peak velocity of 0.237 m s(-1) during depression and 0.269 m s(-1) during elevation). The motion of depression (duration of 0.195 s; kinetic energy of 2.072 x 10(-3) J) could be divided into a phase of acceleration (2.742 m s(-2); +/- 0.28 gn) and a phase of deceleration (2.264 m s(-2); - 0.23 gn), and the terminal excess kinetic energy of depression was absorbed and dissipated by, primarily, the temporomandibular joint. Similarly, the ensuing motion of elevation (duration of 0.182 s; kinetic energy of 2.948 x 10(-3) J) could be divided into a phase of acceleration (3.498 m s(-2); + 0.36 gn) and a phase of deceleration (2.931 m s(-2); -0.30 gn), and the terminal excess kinetic energy of elevation was absorbed and dissipated by, primarily, the dentitions and, secondarily, by the temporomandibular joint. Rapid depression of the mandible appeared to be under the central control of a preprogrammed motor command, and ensuing rapid elevation of the mandible appeared to be under the peripheral control of a segmental and/or transcortical reflex. During rapid depression and elevation of the mandible, the anterior suprahyoid, anterior temporalis, and sternocleidomastoid muscles were myoelectrically active 56%, 73%, and 71% of the time, respectively, and myomechanically active 42%, 59%, and 57% of the time, respectively. Over a follow-up period of 12 months, the studied mandibular motions did not cause injury to the dentitions and temporomandibular joint.

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Section: Instrumentationmentioning

confidence: 99%

Section: Instrumentationmentioning

confidence: 99%

Section: Kinematics/kineticsmentioning

confidence: 99%

Section: Kinematics/kineticsmentioning

confidence: 99%

See 2 more Smart Citations

Kinematic and kinetic observations on ballistic depression and elevation of the human mandible

Christensen¹,

McKay²

2000

J of Oral Rehabilitation

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“…Darüber hinaus werden fasziale Retraktionen der Halsfaszien (mit Verbindung zu den Organfaszien) als Ursache für Irritationen der HWS-Region geschildert [9,20].…”

Section: Studieunclassified