Electromyographic activity of the human lateral pterygoid muscle during contralateral and protrusive jaw movements

• Published in: Archives of oral biology 1999-03, Vol.44 (3), p.269-285
• Main Authors: Murray, G.M, Orfanos, T, Chan, J.Y, Wanigaratne, K, Klineberg, I.J
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Computed tomography; Condyle; Dentistry; Electromyography; Female; Humans; Jaw movement; Jaw Relation Record; Lateral pterygoid muscle; Male; Mandible - physiology; Mandibular Condyle - physiology; Masseter Muscle - physiology; Movement; Neck Muscles - physiology; Pterygoid Muscles - physiology; Range of Motion, Articular; Temporal Muscle - physiology; Temporomandibular Joint - physiology
• ISSN: 0003-9969; 1879-1506
• DOI: 10.1016/S0003-9969(98)00117-4

Understanding of the normal function of the lateral pterygoid muscle is limited. The principal aim here was to determine whether there is a progressive increase in lateral pterygoid activity as the mandibular condyle moves downwards and forwards as would be expected if the muscle is concerned with the precise horizontal positioning of the mandible. In eight humans, recordings were made of the activity of the superior (SHLP) and inferior (IHLP) heads of the lateral pterygoid and the masseter, anterior temporal, posterior temporal and digastric muscles, together with the movement of the palpated lateral condylar pole (JAWS-3D tracking system) during trials of a contralateral and a protrusive jaw movement. Recording sites in SHLP and, in one participant, IHLP were verified by computed tomography. In each participant there was a progressive increase in the rectified and smoothed SHLP and IHLP activity in association with condylar movement during the contralateral and protrusive jaw movement. Further, irregularities in condylar movement, which reflected variations in the rate at which the jaw was moved, were correlated in time with prominent bursts of SHLP and IHLP activity. In all participants there was a consistently high correlation coefficient between the rectified and smoothed SHLP and IHLP activity and condylar displacement during the contralateral or protrusive jaw movements. For example, the mean (±SD) correlation between anterior condylar translation during contralateral excursion and SHLP activity was 0.91±0.09, and for IHLP 0.96±0.02. For the masseter, anterior temporal, posterior temporal and digastric muscles, mean r-values were, respectively, 0.10±0.77; −0.14±0.72; 0.24±0.78; 0.54±0.47. When treated as a group the correlation coefficients for SHLP and IHLP were statistically significantly different from the correlation coefficients for the other muscles treated as a group (ANOVA; p