The aim of this study was to evaluate the associations between head posture (head extension, normal head posture, and head flexion) and anteroposterior head position, hyoid bone position, and the sternocleidomastoid integrated electromyographic (IEMG) activity in a sample of young adults. The study included 50 individuals with natural dentition and bilateral molar support. A lateral craniocervical radiograph was taken for each subject and a cephalometric analysis was performed. Head posture was measured by means of the craniovertebral angle formed by the MacGregor plane and the odontoid plane. According to the value of this angle, the sample was divided into the following three groups: head extension (less than 95 degrees); normal head posture (between 95 degrees and 106 degrees); and head flexion (more than 106 degrees). The following cephalometric measurements were taken to compare the three groups: anteroposterior head position (true vertical plane/pterygoid distance), anteroposterior hyoid bone position (true vertical plane-Ha distance), vertical hyoid bone position (H-H' distance in the hyoid triangle), and CO-C2 distance. In the three groups, IEMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. In addition, the condition with/without craniomandibular dysfunction (CMD) in each group was also assessed. Head posture showed no significant association with anteroposterior head position, anteroposterior hyoid bone position, vertical hyoid bone position, or sternocleidomastoid IEMG activity. There was no association to head posture with/without the condition of CMD. Clinical relevance of the results is discussed.

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A significantly higher level of activity at rest and during swallowing of saliva was observed in the cleft lip and cleft palate group. Similar activity during speech and chewing and swallowing of an apple was observed in both groups. The higher level of activity at rest and during swallowing of saliva in children with cleft lip and cleft palate seems to suggest that upon higher functional demands their activity increases less than in children without clefts. From a clinical point of view, if increased EMG activity at rest and during swallowing of saliva reflects increased force on the maxilla, then our findings may corroborate Bardach's findings (1990) that surgical treatment of cleft lip has an iatrogenic effect on facial growth, although the lack of significant correlation between the cephalometric data and EMG findings in the present study.

The purpose of this study was to determine the effect of canine guidance and group function on supra- and infrahyoid EMG activity in the lateral decubitus position at different jaw posture tasks. The sample included 40 healthy subjects with natural dentition and bilateral molar support, 20 with bilateral canine guidance and 20 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left supra- and infrahyoid muscles for EMG recordings. In the lateral decubitus position, EMG activity was recorded in subjects with canine guidance or group function, during the following jaw posture tasks: A. maximal clenching in the edge-to edge lateral contact position; B. grinding from intercuspal position to edge-to-edge lateral contact position, and C. grinding from edge-to-edge lateral contact position to intercuspal position. Supra- and infrahyoid EMG activity was not significantly different with canine guidance or group function (mixed model with unstructured covariance matrix). Overall comparison of suprahyoid or infrahyoid EMG activity among the three jaw posture tasks studied showed a significantly higher activity during jaw posture task A (clenching) than jaw posture tasks B and C (grinding). Suprahyoid EMG activity was significantly higher during jaw posture task C than B, whereas infrahyoid EMG activity did not present a significant difference between jaw posture tasks C and B. These EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding. The neurophysiological mechanisms involved are discussed.

Objective This study was conducted to compare electromyographic (EMG) activity of superior orbicularis oris muscle between children with repaired cleft lip and cleft palate and children without clefts. Methods This study included 28 children with mixed dentition. They were divided into two groups. The study group included 14 children with repaired unilateral cleft lip and cleft palate, ranging in age from 6 to 12 years, who presented clinically with a short upper lip, abnormal lip seal, and inhibition of sagittal development of the midface as assessed radiographically. The control group included 14 children without clefts ranging in age from 8 to 11 years. All had normal lip seal, nasal breathing, and a clinically normal body posture. Design Bipolar surface electrodes were used for EMG recordings of resting level activity and during swallowing of saliva, speech, and chewing and swallowing of an apple. Results and Conclusions A significantly higher level of activity at rest and during swallowing of saliva was observed in the cleft lip and cleft palate group. Similar activity during speech and chewing and swallowing of an apple was observed in both groups. The higher level of activity at rest and during swallowing of saliva in children with cleft lip and cleft palate seems to suggest that upon higher functional demands their activity increases less than in children without clefts. From a clinical point of view, if increased EMG activity at rest and during swallowing of saliva reflects increased force on the maxilla, then our findings may corroborate Bardach's findings (1990) that surgical treatment of cleft lip has an iatrogenic effect on facial growth, although the lack of significant correlation between the cephalometric data and EMG findings in the present study.

Cephalometric measurements and electromyographic analysis of the superior orbicularis oris muscle were undertaken in 13 children with unilateral cleft lip and palate with a short upper lip length who have undergone surgery in childhood. Initially, cephalometric and electromyographic records were evaluated and again after the subjects had continuously worn, for 4 months, a removable appliance specially designed to avoid the restraining effect of superior orbicularis oris muscle activity over the maxilla. Comparison between pretreatment and posttreatment cephalometric measurements showed a significant improvement in both the sagittal position of the maxilla and the dentoalveolar position. No significant changes were observed in electromyographic activity during rest or when saliva swallowing. Cephalometric changes suggest that the removable appliance used improves the growth of the maxilla.

The study group presented a significant increase in the extension of the head on the neck, forward position of the cervical spine, and a decrease in the curvature of the cervical spine in comparison with the children without clefts. These results are more relevant considering that the study group also presented higher significant values of lower facial height than children without clefts.