Patent ID: 7198486

Claim:
A dental file employed by a dentist while performing a root canal procedure, comprising a shaft including: (a) a shank region, the shank region being adapted to engage a rotary power tool; (b) an abrading region, the abrading region residing on at least some portion of a surface of the shaft, the abrading region being characterized by a first taper that tapers from a relatively large dimension adjacent to the shank region to a first relatively narrow region adjacent to a tip region of the file, the tin region being oppositely disposed from the shank; (c) a discontinuity, the discontinuity being formed within a portion of the shank, the discontinuity being shaped and dimensioned so as to cause the shank to separated from the abrading region when a portion of the abrading region becomes embedded in a human tooth and prior to plastic deformation of the file; and (d) an effective diameter, the effective diameter being a relatively smallest dimension of the shank region after formation of the discontinuity that is defined according to the formula: SBP= ( TS )+( T*V ), where SBP is the effective diameter, in millimeters, of the shank region remaining after formation of the discontinuity, the SBP thereby being a specific value in the range of 0.46 to 0.82 millimeters; TS is a relatively smallest diameter of the tip region of the file in millimeters; T is the first taper of the abrading region, wherein the taper is a percentage of file diameter change for a change in length of the shank region; and V is a variable having a value determined empirically for the file.