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RESEARCH PAPERS

Effect of Hyperactivity of the Lateral Pterygoid Muscle on the Temporomandibular Joint Disk

[+] Author and Article Information
Eiji Tanaka1

Miho Hirose, Toshihiro Inubushi, Yohei Suekawa

Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan

Jan Harm Koolstra, Theo M. van Eijden

Department of Functional Anatomy, ACTA, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands

Ryuji Fujita, Masao Tanaka

Division of Mechanical Science, Department of Systems and Human Science,  Osaka University School of Engineering Science, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

Kazuo Tanne

Department of Orthodontics and Craniofacial Developmental Biology,  Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan

1

Corresponding author.

J Biomech Eng 129(6), 890-897 (Apr 18, 2007) (8 pages) doi:10.1115/1.2800825 History: Received September 07, 2006; Revised April 18, 2007

In this study, the effect of hyperactivity of the lateral pterygoid muscle (LPM) on the temporomandibular joint (TMJ) disk during prolonged clenching was examined with a mathematical model. Finite element models of the TMJ were constructed based on magnetic resonance images from two subjects with or without internal derangement of the TMJ. For each model, muscle forces were used as a loading condition for stress analysis for 10 min clenching. Furthermore, an intermittent increase of the LPM force with intervals of 1 min was applied. In the asymptomatic model, large stresses were found in the central and lateral part of the disk at the onset of clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 min of clenching. When the force of the LPM increased temporarily, the disk moved anteriorly and returned to its original position afterward. In the symptomatic model, large stresses were observed in both the posterior region of the disk and the retrodiscal tissue throughout clenching. Upon temporary increase of the LPM force, the disk was elongated anteriorly, which appeared to be irreversible. These results indicate that hyperactivity of the LPM may be involved in the progression of disk displacement.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

FE models of the asymptomatic (a) and symptomatic (b) joints. These views are anterior 3D view (left) and sagittal 2D view (right). The gray, green, yellow, and blue parts indicate the glenoid fossa, disk, connective tissue, and condyle, respectively.

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Figure 2

Frontal and lateral cephalograms and the rigid link of the mandible with muscle spar elements and rearmost point of occlusal contact

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Figure 3

von Mises stress distribution in the disk (anterior and inferior views) of the asymptomatic joint during prolonged clenching with (b) and without (a) intermittent LPM hyperactivity. The LPM was equally attached to the disk and condylar neck.

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Figure 4

von Mises stress distribution in the connective tissue of the asymptomatic joint (sagittal section) during prolonged clenching with (b) and without (a) intermittent LPM hyperactivity

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Figure 5

The magnitude of the disk displacement in the asymptomatic joint during prolonged clenching: (a) anterior, (b) central, (c) posterior, (d) lateral, and (e) medial points in the disk. Solid curve with closed circles and dotted curve with open circle indicate disk displacements during prolonged clenching with and without intermittent LPM hyperactivity, respectively.

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Figure 6

von Mises stress distribution in the disk (anterior and inferior views) of the symptomatic joint during prolonged clenching with (b) and without (a) intermittent LPM hyperactivity

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Figure 7

von Mises stress distribution in the connective tissue of the symptomatic joint (sagittal section) during prolonged clenching with (b) and without (a) intermittent LPM hyperactivity

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Figure 8

The magnitude of the disk displacement in the symptomatic joint during prolonged clenching: (a) anterior, (b) central, (c) posterior, (d) lateral, and (e) medial points in the disk. Solid curve with closed circles and dotted curve with open circle indicate disk displacements during prolonged clenching with and without intermittent LPM hyperactivity, respectively.

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