[The changes of chewing ability after orthognathic therapy: electromyographic analysis]

OBJECTIVE:The maxillo-facial skeletal deformity can only be corrected through orthognathics that consists of orthodontics and operation.There are various changes in aspect of the bite relationship between upper and lower dentition after orthognathic surgery.The change feature of the chewing efficiency of oral maxillary system can be detected through comparing studying of the contracti on force of chewing muscles before and after surgical operation.METHODS:All 6 patients in this research were diagnosed to be skeletal crossbite.Electromyogram was used to test the change of activity of superficial masseter,temporalis and digastrics.The examination was carried out 1 week before operation and 3 months after the operation. RESULTS:When mandibular is in its rest status,there is no significant difference in the change of muscular activities.when it is active,there is significant difference. CONCLUSION:The chewing ability of masticatory muscles is reduced after orthognathic surgery.The result indicated that there is a negative bite relationship between the upper and lower dentition,the occlusion relationship needs accurate adjustment for gaining stability of oral maxillary system.Therefore,orthodontics after operation is of vital importance.