Effects of Changes in the Anterior Guide on Condylar Movement and EMG Activity of the Inferior Head of the Lateral Pterygoid Muscle

• Published in: Nihon Hotetsu Shika Gakkai Zasshi Vol. 42; no. 4; pp. 680 - 685
• Main Authors: Uchida, Shinji, Kawanishi, Toshio, Sugihara, Shinichiro, Inoue, Hiroshi, Aoki, Seiki, Maeda, Teruta, Ryumon, Hiroshi
• Format: Journal Article
• Language: Japanese
• Published: Japan Prosthodontic Society 1998
• Subjects: anterior guidance; condylar movement; electromyography; lateral pterygoid muscle; protrusive movement
• ISSN: 0389-5386; 1883-177X
• DOI: 10.2186/jjps.42.680

The purpose of this study was to investigate the effects of changes in the anterior guide (AG) on EMG activity of the inferior head of the lateral pterygoid muscle (Lpt). The inclination of the sagittal condylar path (ISCP) in each subject was measured. Values were 20°in sub. 1, 32°in sub. 2, and 43°in sub. 3. Crowns in which the inclination of the sagittal incisal path (ISIP) was equal to that of ISCP (0°), as well as those with ISIP of-10, +10, +20 and + 30° from the ISCP were prepared. The subjects were instructed to perform protrusive sliding movement while wearing each crown. EMG of right Lpt was recorded with condylar movement simultaneously. Condylar movement and mean voltage of EMG (MV) were measured every 0.03 seconds. In sub. 1, the MV did not change significantly with changes in the AG. In both sub. 2 and 3, distance and mean velocity of condylar movement increased and the MV decreased significantly as the AG increased. These results suggested that changes in the AG affected the activity of Lpt on protrusive jaw movement and the AG steeper than the ISCP contributes to smooth condylar movement. However, these differences of effect may have been caused by differences in the ISCP.