Abstract
The purpose of this study was to investigate the effect of tapping, gum chewing and muscle fatigue on the power spectrum and integration of the masticators muscles EMG in 10 patients with mandibular prognathism (5 males and 5 females) and in 10 normal subjects (5 males and 5 females). Muscle fatigue in the anterior temporal and masseter muscles was induced by continuous maximum clenching in intercuspal position for 60 seconds.
1. Tapping and Gum Chewing:
The integration of EMG in mandibular prognathism was lower than that in normal subjects. The MPF (Median Power Frequency) of the masseter muscle was almost the same, but the MPF of the temporal muscle was significantly lower in mandibular prognathism.
2. Continuous maximum clenching:
Muscle activity gradually decreased as time passed during muscle fatigue. The integration of EMG in mandibular prognathism was significantly lower. This suggested that these patients had mandibular dysfunction, and it correlated with the histochemical characteristics of the masseter muscle because the distribution of type 2 fibers was significantly lower in mandibular prognathism.
The MPF gradually shifted to the lower frequencies during muscle fatigue in normal subjects, but in some patients with mandibular prognathism, several abnormal findings, such as shifting to higher frequencies and shifting suddenly to lower frequencies, were recognized. The MPF average was almost the same as that of the masseter muscle but the MPF of the temporal muscle in mandibular prognathism was significantly lower.
The EMG power spectral analysis during muscle fatigue was very useful to evaluate the stomatognathic function in Mandibular Prognathism.
