A Cephalometric/Electromyographic Study of Open-bite/Overbite in Patients of East-African Ethnicity

Objective: Review of the literature reveals that there are disturbances of muscle activity and tongue function in patients with anterior open bite (AOB). However, most studies have been done using Caucasian subjects, even though open bite is more prevalent in black populations. The present pilot study examined jaw muscle activity and tongue pressure in subjects of East-African ethnicity. Methods: Ten subjects (4 male, 6 female, age 10.1-13.2) were recruited. A cephalometric comparison of subjects with and without AOB was performed. Surface electrodes were placed on bilateral anterior temporalis, superficial masseter, superior orbicularis oris and anterior digastric muscles. Electromyograms (EMG) were recorded at rest, maximal voluntary clenching, chewing and swallowing. Tongue pressure during rest and swallowing and maximal bite force were also measured. Results: There was no statistically significant difference between the two groups in cephalometric measures (except in amount of open bite/overbite) and maximum bite force. During chewing, both groups showed similar coordinated activity pattern in muscles, but AOB subjects tended to show more EMG activity in the muscles of balancing side. During clenching, AOB subjects exhibited lower EMG activity compared to controls. AOB subjects also presented a greater amount of anterior tongue pressure during swallowing. Data from tongue pressure at rest was inconclusive. Conclusions: The East-African subjects appear to have neuromuscular and skeletal predispositions to AOB; however their vertical incisor relationships were quite variable. Factors in addition to those investigated may be involved. Supported by UW Royalty Research Fund, UW Orthodontic Alumni Association, and NIDCR grant U54 DE14254.