A 19-year-old female patient with skeletal 3 and anterior openbite malocclusions was treated by a surgical orthodontic approach. A glossectomy was also performed. Cephalometric, electromyographic and kinesiographic records were taken before and after the treatment. The treatment results were as follows: 1. Esthetic improvement in facial profile and static alignment and intercuspation of teeth was obtained. 2. The dimension of the tongue with respect to that of the oral cavity proper measured on the lateral cephalograms revealed a value similar to that determined for the control data after the active treatment. 3. The proportion of reversed strokes with respect to the total chewing strokes increased at the completion of the active treatment both for the right- and the left-sided chewings, but it decreased during the retentive period. 4. At the initial stage, an earlier onset of the masseter muscle activity relative to the temporal muscle group was determined, while the temporalis muscles showed an earlier onset of activity in the postoperative phase. 5. The durations of chewing strokes became shortened in a postoperative phase both on the working and the balancing sides. This observation was particularly significant for the opening and the closing phases. In addition, the proportion of the duration of significant temporalis muscle activity with respect to that of the concomitant chewing stroke increased. 6. Anterior temporalis muscle and masseter muscle activity during clenching performance revealed a value similar to the control data. In summary, the current case suggests that the patients who receive surgical orthodontic treatment require sufficient time to obtain functional readaptation during the retentive period.