All of the movements of a rigid body in three dimensional space may be expressed with six numbers. Three numbers are required to specify the position of an object (i.e. the X, Y, and Z coordinate location) and another three numbers are required to specify rotational orientation (i.e. roll, pitch, and yaw). A commercial device is available which electronically senses each of these variables of three dimensional rigid motion. The first part of this subproject will be to measure the relative rigid motions in dental model simulations of craniofacial surgery and relate these rigid motions to the anatomic bone movements they would produce as registered in a three dimensional cephalometric or CT based surgical simulation. In this way operations wherein large skeletal sections are moved in concert with the teeth, can be evaluated as to whether the desired occlusal change is consistent with the necessary anatomic skeletal change which would be produced. This should aid significantly in more precisely planning such procedures and identifying cases in which more osteotomies between fragments are required to resolve the discrepancy between the desired occlusal and skeletal change. Positioning a three dimensionally mobile fragment correctly under an extremely edematous soft tissue envelope is difficult to do with precision. Use of this six dimensional electronic caliper in the operating room may be of use in correct positioning of bone fragments.