| 摘要 |
The file is made from an elastic wire wound into a spiral. The outer surfaces of some or all of its coils (5a,5b) have an abrasive coating of diamond particles on an adhesive layer. The spiral is made with alternating coils of different diameters (5a,5b,5c), e.g. groups of three coils (5a) with diameters corresponding to that of the tunnel, individual coils (5b) of the same diameter, and groups of coils (5c) of a smaller diameter between them. The groups of coils can be touching or separate, to facilitate cleaning.
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