Superelastic endodontic instrument, method of manufacture, and apparatus therefor
AssigneeKerr Corporation
InventorsFarrokh Farzin-Nia, William Otsen, Gary Garman
Life of this patent
Estimating the term…
Abstract
A superelastic endodontic instrument, such as a file, is formed by grinding a superelastic wire to form a file preform or blank, and rotating a first end of the blank while preventing rotation of a second end of the blank. The file blank is maintained in the austenite phase at least until twisted to form a stress induced martensite which is plastically deformed by the twisting. A heat treatment step may be performed prior to twisting, during twisting or after twisting of the preform. The file blank may be heated by electrical heating methods or by submerging the blank in a heated liquid.
Claims112
An endodontic instrument formed by plastic deformation of a blank having a longitudinal axis and formed from a superelastic material, wherein the instrument is formed by the steps of:
- transforming the superelastic material of the blank into an austenite phase;
- and
- twisting the blank about the longitudinal axis to form an instrument having helically shaped edges.
An superelastic endodontic instrument formed by plastic deformation of a blank having a longitudinal axis and formed from a superelastic material, wherein the instrument is formed by the steps of:
- heating the blank to transform the superelastic material to an austenite phase;
- and
- twisting the blank about the longitudinal axis to form an instrument having helically shaped edges.
A method of forming an endodontic file from a performed wire blank comprising a superelastic material and having a longitudinal axis and a predetermined transverse cross-sectional shape with apices for defining longitudinal edges along a working length of the file, the method comprising the steps of:
- twisting the blank about its longitudinal axis to permanently, helically deform said blank and convert said longitudinal edges into helically shaped cutting edges;
- and
- maintaining the blank in an austenite phase at least until immediately prior to the twisting step.
A method of making a file from a rod formed of a superelastic material and having a first and a second end and a working length therebetween, the method comprising the steps of:
- grinding the rod to form a file preform having a predetermined length, cross-sectional shape and taper along the working length thereof, the cross-sectional shape having corners which define longitudinal edges along the working length;
- and
- twisting the preform to permanently helically deform said preform and form helical shaped cutting edges from said longitudinal edges.
A superelastic endodontic file comprising:
- a shaft formed from a superelastic rod having a working length;
- at least three cutting apices with adjacent cutting apices defining surfaces therebetween, said apices being permanently helically deformed along the working length of said shaft to form helically shaped cutting edges;
- wherein the surfaces of the shaft between adjacent longitudinal cutting edges define elongated helical surfaces which are flat when viewed in transverse cross section.
A superelastic endodontic file comprising:
- a shaft formed from a superelastic rod having proximal and distal ends with a working length therebetween, said proximal end including a handle section and said distal end including a tip;
- four or more cutting apices helically arranged about said shaft along the working length;
- wherein the working length of said shaft includes a transverse cross-sectional area which is substantially rhomboidal in shape.
An endodontic file having a predetermined transverse cross-sectional shape including corners, the file comprising:
- integral working length and handle sections formed of a material exhibiting superelasticity above an austenitic finish temperature Af of the material with said working length having the predetermined transverse cross-sectional shape,
- said working length being twisted about its longitudinal axis to permanently form helical cutting edges at the corners thereof.
An endodontic file comprising:
- a shaft including a working length portion formed of a material exhibiting superelastic characteristics, said working length portion having a predetermined transverse cross sectional area, a longitudinal axis, and a plurality of apices defining cutting edges,
- said working length portion being permanently plastically deformed by twisting about its longitudinal axis to form said cutting edges at the apices thereof.
Apparatus for forming an endodontic instrument from a superelastic rod-shaped blank, the apparatus comprising:
- a linear motion mechanism including a clamping element for holding a portion of said blank and moving said clamping element along said blank;
- a rotary motion mechanism for holding and rotating said instrument, said rotary motion mechanism being operatively coupled to said linear motion mechanism for rotating said blank as said clamping element moves therealong to form a helically fluted instrument;
- and
- a source of heat disposed proximate said linear and rotary motion mechanisms for heating said blank at least prior to operation of the linear and rotary motion mechanisms.
Dependencies are inferred from the claim text.