The relation between anterior guidance and condylar path was studied three-dimensionally utilizing a kinematic priciple and experimental data. Kinematic formulae that compute the threedimensional directional angles of incisal path during eccentric mandibular movements from the measured data of condylar path were presented. The methods for determining the angle of hinge rotation of the mandible and sagittal deviation of the working condylar path were studied, both of which are necessary for accomplishing the above computation.
The angle of hinge rotation of the mandible was caused by making anterior guidance steeper than condylar path, and was related analytically as a factor which causes disclusion. The amount of disclusion is found to approximate the deviation in the condylar path in a mechanism to avoid occlusal interferences. The cusp shape component was another factor which produced disclusion.
The amount of disharmony in canine guidance influenced sagittal deviation of the working condylar path, and if canine guidance was made so that the amount of disharmony was negligible, then the working condyle moved outward along the terminal hinge axis without any sagittal deviation. The clinical procedures for patient treatment were described.

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Human dental root surface area is closely related to the sustainability of the periodontal membrane against forces exerted on the teeth, such as the biting, tongue and buccal forces. In Prosthetic Dentistory in particular, in selecting the clasped tooth or abutment tooth for partial denture and crown bridge, a knowledge of the sizes of the root surface area and their relations is as important as the analyses of the morphology and sizes of the teeth, crown-root ratio, implaned conditions and attachment direction. The forms of dental roots, however, are small and irregular and are difficult to measure. To date, some reports have been made on the subject but leave something to be desired. The author, therefore, devised a new surface measuring method with a use of silver plating for irregular-shaped test pieces. A total of 100 model test pieces comprising 10 varieties each of 3 types were measured by the method. After making examinations of the theoretical values calculated mathematically in advance and the errors in the actual measuring, a total of 280 extracted natural teeth, 20 pieces each from each position, were measured. The results obtained were were as follows : (1) Duplicates of the test pieces to be measured were made with epoxy resin and non-electro plating and electro plating were done on the surface. The surface area (A) was obtained by applying to the formular A≒k/(ω・r), the values ascertained of plating weight (k), plating thickness (ω) and specific gravity of plating (r). (2) The surface area of the model test pieces were measured by the plating method and the measurements were compared with the theoretical values. As a result, an average error of 0.7% was obtained. (3) The root surface areas obtained were : of the upper jaw, central incisor : 218.48mm^2, lateral incisor : 192.79mm^2, canine : 316.56mm^2, first premolar : 284.94mm^2, second premolar : 233.33mm^2, first molar : 456.06mm^2, second molar : 428.77mm^2. Of the lower jaw, central incisor : 167.39mm^2, lateral incisor : 180.30mm^2, canine : 278.89mm^2, first premolar : 206.06mm^2, second premolar : 225.24mm^2, first molar : 418.50mm^2, second molar : 374.61mm^2. (4) The ranks of sizes in descending order were : of the upper jaw, first molar, second molar, canine, first premolar, second premolar, central incisor and lateral incisor. Of the lower jaw, first molar, second molar, canine, second premolar, first premolar, lateral incisor, and central incisor. (5) For any position, the root surface area of the tooth in the upper jaw was greater than that of the corresponding tooth in the lower jaw.

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