Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep

We previously reported that the wearing of cervical headgear induced forwar d displacement of the mandible in awake subjects. However, it was unclear w hether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyng eal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed co nsent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiraton during stage 1 to 2 non-rapid-eye-movement sleep. The Wil coxon signed-rank test was used for a statistical analysis. The amount of j aw opening was significantly decreased by the wearing of the cervical headg ear (P < .05), although no significant anteroposterior mandibular displacem ent was induced. The sagittal dimension of the upper airway was significant ly reduced (P < .05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervica l headgear (P < .05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results s uggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anterop osterior displacement of the mandible.