Gnathostat

GNATHOSTAT (from Greek gnathos-jaw and Latin status-position), an instrument by means of which the position of the jaw-tooth apparatus is determined in relation to the main planes of the skull, i.e., in relation to the so-called Frankfurt horizontal plane, passing through the external auditory opening and the lower edges of the orbit, the sagittal plane, passing along the midline of the head from front to back, and the frontal plane, passing through the outer edges of the orbit perpendicular to the horizontal plane (see figure). Introduced by van Loon and improved by Simon. The main parts are: an impression tray for obtaining a mold of the jaw and teeth, a metal rod 20 cm long, and a semicircular strip moving up and down along the rod with 4 arrows. These arrows are movable and can be fixed in any position. They are placed on the orbital points and on the points of the external auditory opening (tragus). Subsequently, with the help of additional instruments, the data obtained are transferred to a plaster model and in this way lines are obtained, the position of which indicates various anatomical deviations. The accuracy of the data from the G. is disputed by the American school of orthodontists.