This study combined the use of cephalometrics and overnight polysomnographic monitoring to analyze the effects of a dental appliance on airway, sleep and respiratory conditions in 10 patients with obstructive sleep apnea. The findings indicated that horizontal and vertical mean changes in mandibular position while the appliance was worn were 1.73 mm and 9.30 mm, respectively, the mean superior airway space increased by 2.80 mm (P < 0.01), while the mean middle airway space increased by 6.75 mm (P = 0.01), the inferior airway space, however, didn't change significantly when the appliance was worn. The average Apnea Index decreased by 15.98 events per hour when the appliance was worn (P < 0.01), the average Respiratory Disturbance Index decreased from 39.43 to 6.62 events per hour in 9 of 10 patients (P < 0.01, one patient didn't have recording of hypoventilation). the lowest SaO2 value increased from 73.87% to 85.50% (P < 0.01). The reduction in the rate of airway obstructive events is attributed to the effect of appliance on the orophargneal structures. The dental appliance is a conservative, successful treatment alternative that could benefit patients with obstructive sleep apnea syndrome.