IADR Abstract Archives
Comparison of Intramuscular and Surface EMG Recordings of the Masseter Muscle
Objectives: Reorganization of the recruitment pattern of motor units (MUs) represents the most plausible explanation for therapeutic effects of oral splints in TMD pain of muscular origin. Aim of this study was to investigate the electromyographic (EMG) activity patterns of the masseter by means of EMG mapping with intramuscular and surface electrodes.
Methods: Twenty healthy subjects (average age: 24.7±2.5y.) were involved in the study. The subjects bit with submaximal force on intraorally fixed, fluid filled pads, connected with a force measuring system, which simultaneously provided a visual feedback. The vertical jaw relation (VR) could be altered (2-4-6mm) by adapting the volume of the pad-filling. The level of submaximal bite force was individually determined.
The EMG activity of the right masseter was recorded simultaneously by intramuscular (iEMG) and surface (sEMG) electrodes in three different areas (anterior/medial/posterior). In addition, the EMG activity during biting in intercuspation (ICP) was recorded under identical experimental force conditions. Root mean square values of all muscle areas for iEMG as well as for sEMG were calculated. The data were normalized with maximum bite force. sEMG and iEMG values were compared with non-parametric tests.
Results: The normalized EMG values did not differ significantly between iEMG and sEMG for all areas and across all tasks, except for the median part of the masseter for biting in ICP and with 2 mm VR (p<0.05).
Comparison of the values across the tasks showed a statistically significant difference (p<0.05) between ICP and the 4 and 6 mm VR in all regions of the masseter. This could be observed for both, iEMG and sEMG recordings.
Conclusions: The study found that changes in muscle activity, induced by small changes of the lower jaw position, as also caused by splints, indicate comparable EMG patterns with intramuscular and surface electrode mappings.
Methods: Twenty healthy subjects (average age: 24.7±2.5y.) were involved in the study. The subjects bit with submaximal force on intraorally fixed, fluid filled pads, connected with a force measuring system, which simultaneously provided a visual feedback. The vertical jaw relation (VR) could be altered (2-4-6mm) by adapting the volume of the pad-filling. The level of submaximal bite force was individually determined.
The EMG activity of the right masseter was recorded simultaneously by intramuscular (iEMG) and surface (sEMG) electrodes in three different areas (anterior/medial/posterior). In addition, the EMG activity during biting in intercuspation (ICP) was recorded under identical experimental force conditions. Root mean square values of all muscle areas for iEMG as well as for sEMG were calculated. The data were normalized with maximum bite force. sEMG and iEMG values were compared with non-parametric tests.
Results: The normalized EMG values did not differ significantly between iEMG and sEMG for all areas and across all tasks, except for the median part of the masseter for biting in ICP and with 2 mm VR (p<0.05).
Comparison of the values across the tasks showed a statistically significant difference (p<0.05) between ICP and the 4 and 6 mm VR in all regions of the masseter. This could be observed for both, iEMG and sEMG recordings.
Conclusions: The study found that changes in muscle activity, induced by small changes of the lower jaw position, as also caused by splints, indicate comparable EMG patterns with intramuscular and surface electrode mappings.