Patent ID: 7704075

Claim:
A flexible dental instrument for use in drilling a root canal, and the dental instrument being designed to be mechanically driven by an electric motor, the dental instrument ( 10 ) being flexible and comprising: an end section ( 11 ) for mounting in a chuck driven by an electric motor, a proximal region ( 14 ) adjacent to said end section ( 11 ), a central region ( 13 ) extending from said proximal region, and a distal region ( 12 ) extending from said central region ( 13 ) for guiding the instrument through a root canal, and an envelope ( 20 ) comprising the proximal region, the central region and the distal region and the envelope defining an axial length and having a generally inverted cone shape, with a widest portion of the envelope ( 20 ) corresponding to the distal region ( 12 ) and a smallest portion of the envelope ( 20 ) corresponding to the proximal region ( 14 ), wherein the dental instrument further comprises a junction region ( 17 ), located between the proximal region ( 14 ) and the end section ( 11 ), and the junction region ( 17 ) comprises an area of the envelope ( 20 ) having a minimum thickness which is designed to break in the event that a predetermined drive torque is applied to the envelope ( 20 ) during use of the dental instrument, and a leading end of the end section ( 11 ) tapers toward and joins with the junction region ( 17 ), and the central region ( 13 ) is polygonal and comprises hollowed flutes ( 16 ) with sharp cutting edges that are generally helical.