Geometric (Non-anatomic) School
Denied the existance of condylar axes and disregarded the condylar paths as influences on occlusion, instead claiming that the articulation of teeth guides the mandible during mastication.
Condylar (Anatomic) School
Adjustable condylar guides - Average value instruments
“Equilateral Triangle Theory” 1864
William G. A. Bonwill - The size of the mandible is equal to 10 cm (4 inches) from condyle to condyle and from each condyle to the incisor point.
Francis H. Balkwill - Is formed between the occlusal plane and Bonwill triangle (~26 ̊).
Ferdinand Graf von Spee
“The relationship between the curved arrangements of the occlusal planes of natural teeth and the corresponding curves of the condylar paths.”
Curve of Spee
the molar masticatory surfaces lie on the same arc of a circle. The posterior continuation of which touches the most anterior point of the condyle.
The location of the axis of that cylinder’s curvature is at the level of the horizontal mid-orbital plane.
The steeper the path of the condyles, the more pronounced the tooth curve would be, because both have the same radius.
The space that occurs between the maxilla and mandible during protrusion. **Christensen’s Rational articulator with plaster casts and wax occlusion rims. Empty space (now disclusion). Creates empty space in the back. This space when jaw moved forward is referred to as the Christensen phenomenon. He then created an articulator to prove his work.
George Monson -
Monson presented for the first time a method for setting denture teeth, using Bonwill’s equilateral triangle conforming to the surface of a sphere.
Made mandibulo-maxillary instrument (articulator). This works on principle of the sphere.
4 sticks to 6 eq. triangles
Monson center of rotation
Located at glabella. First time spherical motion is considered.
Curve of wilson
George wilson. In the theory that occlusion should be spherical, the curvature of the cusps as projected on the frontal plane expressed in both arches; the curve in the lower arch being concave and the one in the upper arch being convex.
Conical theory of mandibular movement. Center of rotation at back of skull. External occipital protuberance is considered as the anatomical rotation center of mandible. In essence, he flipped the triangles and mirrored them.