Cephalometric and electromyographic study of patients of East African ethnicity with and without anterior open bite

A review of the literature showed that there are disturbances of muscle activity and tongue function in patients with anterior open bite (AOB). However, most studies have had white subjects, even though open bite is more prevalent in black populations. In this pilot study, we examined jaw muscle activity and tongue pressure in East African black subjects.

Ten subjects (4 boys, 6 girls; ages, 10.1-13.2 years) were recruited. A cephalometric comparison of subjects with and without AOB was performed. Surface electrodes were placed on the bilateral anterior temporalis, superficial masseter, superior orbicularis oris, and anterior digastric muscles. Electromyograms were recorded at rest, maximal voluntary clenching, chewing, and swallowing. Tongue pressure during rest and swallowing, and maximal bite force were also measured.

There was no statistically significant difference between the 2 groups in cephalometric measures (except in amount of open bite and overbite) and maximum bite force. During chewing, both groups showed similar coordinated activity patterns in the muscles, but the AOB subjects tended to show more electromyographic activity in the muscles of the balancing side. During clenching, the AOB subjects exhibited lower electromyographic activity compared with the controls. AOB subjects also had greater anterior tongue pressure during swallowing. Data from tongue pressure at rest were inconclusive.

East African blacks appear to have neuromuscular and skeletal predispositions to AOB, but their vertical incisor relationships are variable. Factors in addition to those investigated might be involved.