Pharyngeal Effects: The protrusion of the mandible by prosthetic appliances ("Esmarch-prosthesis") may be a simple therapy for obstructive sleep apnea, but is effective only in rare cases. Aim of this study was the cephalometric investigation of pharyngeal changes by mechanic-/prosthetic mandibular protrusion in respect of the amount of protrusion. Cephalometric investigation was performed in 46 patients before and after mandibular protrusion, subdivided into 3 groups with protrusion of less than 7 mm, 7 to 10 mm, and more than 10 mm. A significant pharyngeal enlargement was found in all patients, but there was no correlation between the amount of protrusion and the amount of pharyngeal enlargement. Mandibular protrusion of more than 10 mm did not necessarily lead to more pharyngeal enlargement. A reliable prognosis of pharyngeal enlargement in respect of the amount of mandibular protrusion is not possible by cephalometric evaluation, even less a reliable prognosis of treatment success in respect of obstructive sleep apnea.