| 摘要 |
A set of root canal drill bits, each comprising a tapering rod (1) with at least one spiral cutting edge (2), has the diameters (D1) of the cutting tips and the diameters of the bits at the start of the cutting edges varying in geometrical progressions, each in the same proportion. In variants of the design, the proportion of the geometrical progression in which the tip diameters increase can be greater or smaller than the corresponding proportion for the diameter at the start of the cutting edges. The bits in the set can be made from different material or be subjected to different thermal treatments to give them all the same flexibility.
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