The present disclosure provides computing device implemented methods, computing device readable medium, and molds for filling undercut areas of teeth relative to an axis of placement. Filling undercut areas of teeth relative to an axis of placement can include calculating an undercut area of a tooth relative to an axis of placement of part of a dental appliance over a number of teeth and a height of contour that is defined based on the axis of placement. Filling undercut areas of teeth relative to an axis of placement can also include filling in a part of the undercut area of the tooth with a virtual filler wherein the undercut is filled to within a threshold distance from the tooth that is defined relative to the axis of placement and the height of contour.