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This study established a new method of quantitive analysis on the form of abutment teeth prepared with natural teeth at Random Position (R. P.) under clinical situation.The subjects for this study which were the maxillary first premolars on the right and left side andthe cases of indication of extruction conveniently under orthodontic treatment were evaluated.The preparations were the chamfer type for full cast crowns on the right side and the full-shoulder type for full-bake type porcelain fused to metal crowns on the left side.Further, those data were compared with the average data of ten abutment teeth prepared withmelamine-resin teeth on a mannequin by the same operator at R.P. to evaluate this new method ofanalysis.Those data could be compared under the same standard and the form of abutment teeth preparedwith natural teeth were similar to that with melamine-resin teeth. On the side, some factors whichwere considered to influence the teeth preparation were apparent.As a result, this new method could be used for analysis of the form of abutment teeth preparedwith natural teeth.

Following are the results of a study made on the influence to the prepared tooth form, when the abutment tooth preparation with full cast crowns are done for the Maxillar Left Fixed Prosthodontics three-unit bridge in Random Position. The prepared teeth arethe Second Premolar and the Second Molar (The“Second Premolar”is abbreviated to “5” and the “Second Molar”is abbreviated to “7”).1. The reduced extent of occlusal surface was excessively large at 5 and 7 buccal cusps, while it was excessively small at Central grooves.2. The reduced extent of axial surface was excessively small at 5 and 7 all surfaces.3. The reduced extent of subgingiva tended to be shallower than the designated depth of 1.0mm at the all portions.4. As for the degree of axial taper, its made steeper toward the buccal and distal surface both 5 and 7.5. As for the relative degree of axial taper, it get the largest in degree on bothsides between5 medial surface and 7 distal surface.

The purpose of this study is to mesure the three dimentional distotions and displacements in the Non-precious (Ni-Cr) ceramometal fixed bridge using the pre-soldered method.Following conclusions were obtained as a results.1. During the Pre-soldering stage, the distotion of soldered bridge frame (the potion was made with one-piece cast method) are minimal.2. During the Pre-soldering stage, the curve of fixed bridge frame was slight opened on horizontal plane, but on the vertical displacement was larger than others.

1. The state of inclination and the change under various conditions of the imaginary axis of the tooth crown of upper jaw anterior teeth can be determined by the image measuring system and method of this study. 2. The measurement error of this system was not more than 0.3 degree. This value was sufficient for the purpose of this study. 3. The imaginary axis of the tooth crown of anterior teeth was determined on the study cast with 1 to 3 degrees in mesiodistal direction and 2 to 4 degrees in labiopalatal direction as standard deviation. 4. The imaginary axis of the tooth crown of anterior teeth was determined toward labial in the random position and toward patient's right and palatal in Standing Posture. 5. It was confirmed that the determination of the imaginary axis of tooth crown was effected by the position of the patient relative to the operator, limitation or direction of view, and approach direction.