Effects of random position on the abutment form for a full cast crown. The right upper first molar

Abstract

The right upper first molar was prepared as a test tooth for the outside abutment for a full cast crown in the random position (R. P.). The characteristics of the reduction and the total amount of time required for the preparation of the abutment were examined. In comparison with the results obtained in the home position (H.P.) by Ishizuka, the following results were obtained.1. In terms of the effect of R. P. and H. P. on the form of the abutment, a significant difference from the indicated degree was noticed in the taper degree, particularly on the axial surface; the imaginary crown axis was inclined to the distal proximal side in R. P. and inclined to the mesial proximal side in H. P.2. In comparison with the time required for the preparation of the abutment between R. P. and H.P., no large difference was noticed in the time of operation and the total time of the air turbine, while the time of non-operation in R. P. was about 1/2 of that in H. P.; the ratio of nonoperation time to total time in R. P. was about 1/2 of that in H. P.