Object Record

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Object/Catalog Number FIC10.3.11
Object Name Articulator, Hall Alligator
Collection Miscellaneous Articulators & Related Equipment
Object Category 15: Dental Materials, Tools & Equipment
Object Sub-category Prosthodontics-Crown, Bridge & Dentures
Date 1917
Description The second patented version and production model of the Hall articulator known as the "Alligator," designed by Rupert E. Hall, Philadelphia, PA and patented March 6, 1917. U.S. Patent No.: 1218178. Articulator was designed with a provision for a facebow. Old ID tag attached: "No. 17 Hall." Bears entwined SSW logo of the S.S. White Dental Manufacturing Company. Articulator is missing its incisor guide pin.
Material Brass and steel
Length (in) 10
Width (in) 4.75
Height (in) 3.875
Inscription Text SSW
Inscription Type Manufacturer's Mark
Inscription Location Base
Condition Fair


The Hall "Alligator" Articulator (Production Model)

Designed by: Rupert E. Hall

Manufactured by: S.S. White Dental Manufacturing Company, Philadelphia, PA

U.S. Patent No.: #1,218,178

Patent Date: March 6, 1917

This commercial model of Hall's "Alligator" is based on the principles outlined in the earlier prototype.

It was constructed to conform to Hall's "Conical" theory of mandibular movement. The theory stated that, if two equilateral (Bonwill) triangles were placed back to back, they would share the condylar (opening/closing) axis as a common base. The apex of the anterior triangle would be located at the incisal point and the apex of the posterior triangle would be located in the region of the external occipital protuberance. Finally, the posterior point would be the lateral rotation center of the mandible. However, the lateral rotation center of this manufactured instrument was located on a level with the occlusal plane and more adjustment features were added to accommodate differences in patients. Unlike the first version, this articulator was commercially available.

Source: Articulator Archives, University of Texas, Dental Branch Houston


In November 1916, Rupert E. Hall received his first patent for an articulator, a device that has been unceremoniously nicknamed the "Alligator." It was patented as a "single rotation center" device, but Hall provided no instructions for its use. This instrument predated his later model based on his "conical" theory of occlusion. The "Alligator" was the first articulator to include an incisal guide table with adjustable lateral wings. The illustration appearing in this patent (Fig 11) has been misinterpreted as the first version of the "Alligator." In fact, it is a "perspective view of an articulator…showing diagrammatically the principles upon which the articulator is based."16 On Hall's second articulator (March 1917), a revised version of the "Alligator," the incisal pin was designed to function within a 45-degree cup17 (Fig 12).

Edgar N. Starcke, DDS. "The History of Articulators: The Appearance and Early Use of the Incisal-pin and Guide," Journal of Prosthodontics, Vol 10, No 1 (March), 2001: pp 52-60.
Related Publications U. S. Patent No.: 1218178 (March 6, 1917)
U. S. Patent Documentation - Google Patents:

Edgar N. Starcke, DDS. "The History of Articulators: A Critical Review of Articulators Basedon Geometric Theories of Mandibular Movement, Part II: Rupert Hall’s Conical Theory." Journal of Prosthodontics, Vol 11, No 3 (September), 2002: pp 211-222.

Edgar N. Starcke, DDS. "The History of Articulators: The Appearance and Early Use of the Incisal-pin and Guide," Journal of Prosthodontics, Vol 10, No 1 (March), 2001: pp 52-60.
Number of images 1.0
Catalog date 2010-03-24
Dimensions H-3.875 W-4.75 L-10 inches
Caption Hall Alligator Articulator
Condition Notes Incisor guide pin missing.
Inscription Technique Stamped
Made United States: S. S. White Dental Manufacturing Company, Philadelphia, PA