Measurer for angle of mandible
To give an indication whether the open bite is skelletal or muscular of origin.
With open mouth behaviour and a low position of the tongue in rest, there possibly can develop a more vertical growth of the mandible (see Vertical growth of the face). A normal angle of mandible is between 85 and 120 degrees. There are several opinions over when to speak of an aberrant angle of mandible. The American orthodontist C. Steiner says between 120 and 130 degrees. Another American orthodontist, J. Jarabak, says between 123 and 137 degrees. For speech pathologists it is safe to hold to 120 degrees.