Dynamic Study on the Force Distribution of Various Forms of Full-Cast Crown Abutment Teeth

Abstract

There are many studies on the full cast crown, but the all-out dynamic studies foraxial, ocolusal and margunal form, that is very important factors, have not been find. The author tries to analyze the dynamic effect of differences of full cast crown abutment on the abutment, then the two-dimesnional photoelastic studies are carried out. The maxillar bicuspid for specimens is bucco-lingual synmetrical form, and the specimens being enlarged the three times of this teeth. are made by the B-hardner #901. The photoelastic apparatus, product of the Riken-keiki Co., is used for this study. The load direction is arranged at the long axis of specimen, the monochromatic fringe photographes are taken and analyzed.The abutment forms of full cast crown consist of three factors, that is the axial angle (5, 10, 20 and 30 degrees), the cusp angle (0, 10, 20, 30 and 40 degrees) and the marginal form (knife edge type, chamfer edge type, bevel edge type, bevel-shoulder edge type and shoulder edge type), and are carried out to analyze by the two-dimensional photoelastic test. Futhermore, the specimens with the axial angle of 5 degrees the cusp angle of 30 degrees are preparated of three marginal forms (knife edge type, chamfer edge type and shoulder edge type) and they are analyzed. The dynamic effects of differences of abutment forms on the abutment are investigated and the following conclusions are obtained.1. Regarding the axial angles, the each specimen with 5, 10, 20 and 30 degrees is researched. The maximum stress concentration in each specimen is observed at the pulp horn. Its value is tend to increase according as the axial angle increases. Therefore, it is concluded that theless the axial angle is, the more the abutment is dynamically. Consquently, the best axial angle is 5 degrees.2. As regards the cusp angle, the each specimen with 0, 10, 20, 30 and 40 degrees is studies. The strees concentration is observed at the pulp horn and margin. It is find that the more the cusp angle increases, the less its values are. Then, the cusp angle is best according as it increase, especially, it is effect as to decrease the stress concentration at the pulp horn and margin.3. As for the marginal forms, the specimens with knife edge type, chamfer edge type, bevel edge type, bevel-shoulder edge type and shoulder edge type are investigated. Regarding the stress concentration at the pulp horn, the knife edge type is minimum, and the chamfer edge type, bevel edge type, bevelshoulder edge type and shoulder edge type are increased in order of magnitude. Consquently, the knife edge type is best, the chamfer edge type, bevel edge type, bevel-shoulder edge type and shoulder edge type are in order of magnitude.4. As regards the specimen with the axial angle of 5 degrees and the cusp angle of 30 degrees being preparated for the marginal forms of knife edge type, chamfer edge type and shoulder edge type, the knife edge type is best. The chamfer edge type and shoulder edge type is in order of stability. In case of the shoulder edge type with the cusp angle of 30 degrees, the stress of margin and pulp horn is remarkably decreased. As to use of this type, this is careful consideration.