The Facebow Essay

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THE FACEBOW PURPOSE: The function of the facebow is to record the relationship of the maxillary arch to the horizontal axis of rotation of the mandible (sometimes referred to as the terminal hinge axis). Three points of reference are necessary to order to designate a plane. The points needed in order to utilize a face tow are: 1 &2 -- The two skin points athat describe the exact or abbitary points where the horizontal axis passes through the skin serve to designate two of the points of the plane of orientation of the facebow. When an earpiece facebow is used, the two points where the ear rods of the facebow enter the external auditory meatus of the ear serve as the two points of orientation. 3--the third point of reference is located on the face at a point that will assist the convenient location of the maxillary cast between the upper and lower members of the articulator. This point of reference may vary depending on which brand of articulator is used. Having completed the facebow registration, the maxillary cast can be mounted in the articulator in relationship to the condylar mechanism and the horizontal plane of reference. TYPES OF FACEBOWS There are two basic types of facebows: 1. Simple facebow (arbitrary or earpiece) 2. Hinge axis transfer bow (kinematic) The simple facebow can be utilized to transfer the relationship of the maxillary arch and an average intercondylar axis. The axis can be designated either arbitrarily (average measurement along the Frankfort Horizontal Plane) or by the position of the ear rod in the ear canal. The difference in the position of the ear bow position is accommodated for by the design of the articulator and its earbow receiver points. A more precise location of the horizontal axis can be made with a kinematic registration of this axis using a kinematic registration bow. The exact location of the points where the
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