| 摘要 |
The invention concerns a drill assembly for preparing a prosthetic crown-receiving tooth, wherein said drills (1) are of the type comprising an active part and at least an inactive part. Each of the drills (1) comprises a distal end (12) shaped like a sphere portion having an inactive part (13) and an active part (11), one of which consists of a spherical cap in apical position with a small circle (14) having a radius much smaller than its bending radius.
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