Abstract: A digitally-based method is described for the design and production of customized removable dental appliances. The plastic component of custom appliances is designed using software, and milled directly over a plaster model of the dentition. A patient's upper, lower, and bite-registered arches are digitized, registered to a bite or centric occlusion position, and articulated in software using either an average geometry or the geometry of a specific articulator. Appliance design is performed by defining the desired plastic surfaces and margins as dictated by the relative movement and positions of the arches as functionally required for a specific appliance. Standard CAM software is used to read the design file and command a multiaxis machine center to mill the plastic while directly on a plaster model.