| 摘要 |
The invention concerns a drilling instrument ( 10 ), in particular for drilling dental root canals comprising a base ( 11 ) and a guide section ( 13 ) as well as a polygonal cutting section ( 12 ). Said cutting section includes several helical cutting edges ( 17 ) defining an envelope ( 15 ). The flutes ( 14 ), which are the surfaces linking in the cutting edges, are cut out such that part of them define clearance zones ( 16 a) alternately arranged between the drilling zones ( 16 b). In the central part of a clearance zone ( 16 a), the cutting edges ( 17 ) are all arranged recessed inside the envelope ( 15 ), in the central part of the drilling zone ( 16 b), said cutting edges are all arranged on the envelope, and in a zone intermediate between a clearance zone ( 16 a) and an adjacent drilling zone ( 16 b), at least one cutting edge is on the envelope and at least one cutting edge is recesses inside the envelope. |
