Disclosed herein are methods of manufacturing an oral appliance, the method comprising the steps of: a) importing into a computer aided design (CAD) computer program a digitized data set obtained from a three-dimensional scan of a patient's dentition; b) preparing a three-dimensional electronic model of the patient's dentition; c) subtracting the three-dimensional electronic model of the patient's dentition from an image of a solid block to obtain an appliance data set; and d) manufacturing a dental appliance in accordance with the appliance data set. Also disclosed are devices made by the above method, and methods of treating a condition, for example a sleep breathing disorder, by using a device made by the above method.