Rupert E. Hall
S.S. White Dental Manufacturing Company, Philadelphia, PA
This articulator has two pivotal points. The lower pivotal point represents the opening and closing axis of the glenoid fossa. The upper pivotal point was claimed to be in the vicinity of the occipital protuberance and provides the lateral rotation center. This design is based upon Hall's “conical” theory, an arbitrary theory of mandibular movement and was inspired by Monson's “Spherical” theory of 1898. The vortex of the cone is located at the upper pivotal point and the maxillary denture teeth would be set coincident with a segment of an arc of the inner surface of an 8-inch cone. The lateral wings of the incisal guide table are 45-degrees to the horizontal plane. This is the “generating angle” of the cone. This mounting jig was designed by Hall for orienting the casts to the articulator at the level of the lower pivotal point (hinge axis). He claimed it eliminated the need to use a face-bow.
This instrument adds several structural improvements to the "Automatic Anatomic Articulator” offered by M.M. House, including an unobstructed posterior view of the mounted casts. None of the basic features reflecting the conical theory were altered. House also suggested a mechanism for longitudinally adjusting the lower cast holder for grinding teeth to compensate for retrusive movements of the mandible.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.