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Endodontic instruments for use in performing root canal therapy on a tooth are disclosed. In one form, the instruments include an elongate shank having a cutting edge extending from a distal end of the shank along an axial length of the shank. The shank comprises a titanium alloy, and the shank is p

Endodontic instruments for use in performing root canal therapy on a tooth are disclosed. In one form, the instruments include an elongate shank having a cutting edge extending from a distal end of the shank along an axial length of the shank. The shank comprises a titanium alloy, and the shank is prepared by heat-treating the shank at a temperature above 25° C. in an atmosphere consisting essentially of a gas unreactive with the shank. In another form, the endodontic instruments have an elongate shank having a cutting edge extending from a distal end of the shank along an axial length of the shank. The shank consists essentially of a titanium alloy selected from alpha-titanium alloys, beta-titanium alloys, and alpha-beta-titanium alloys. The instruments solve the problems encountered when cleaning and enlarging a curved root canal.

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1. An endodontic instrument for use in performing root canal therapy on a tooth, the endodontic instrument prepared by a method comprising: (a) providing an elongate shank comprising a superelastic nickel titanium alloy, the elongate shank having a first portion including a cutting edge extending fr

1. An endodontic instrument for use in performing root canal therapy on a tooth, the endodontic instrument prepared by a method comprising: (a) providing an elongate shank comprising a superelastic nickel titanium alloy, the elongate shank having a first portion including a cutting edge extending from a distal end of the shank along an axial length of the shank and a second portion without a cutting edge; and(b) after step (a), heat-treating the entire shank,wherein the heat-treated shank has increased angular deflection compared to a shank of same composition and size not treated in accordance with step (b), andwherein the heat-treated shank has an angle greater than 10 degrees of permanent deformation after torque at 45° of flexion when tested in accordance with ISO Standard 3630-1. 2. The endodontic instrument of claim 1 wherein the angular deflection is determined by a study of torsion reported in degrees of deflection performed in accordance with ISO Standard 3630-1 Dentistry—Root-canal instruments—Part 1: General requirements and ANSI/ADA Specification No. 28, Endodontic files and reamers. 3. The endodontic instrument of claim 2 wherein the heat-treated shank has increased fatigue life compared to a shank of same composition and size not treated in accordance with step (b). 4. The endodontic instrument of claim 1 wherein the heat-treating is at a temperature from 300° C. up to but not equal to the melting point of the nickel titanium alloy. 5. The endodontic instrument of claim 1 wherein the heat-treated shank has 18% or greater increased angular deflection compared to an endodontic instrument of same composition and size not treated in accordance with step (b). 6. The endodontic instrument of claim 1 wherein step (b) comprises heat-treating at a temperature dependent on a time period selected for heat exposure. 7. The endodontic instrument of claim 1 wherein step (b) comprises heat-treating the shank in an atmosphere that comprises a gas selected from the group consisting of helium, neon, argon, krypton, xenon, and radon. 8. An endodontic instrument for use in performing root canal therapy on a tooth, the endodontic instrument prepared by a method comprising: (a) providing an elongate shank comprising a superelastic nickel titanium alloy, the elongate shank having a first portion including a cutting edge extending from a distal end of the shank along an axial length of the shank and a second portion without a cutting edge; and(b) after step (a), heat-treating the entire shank,wherein the heat-treated shank has increased fatigue life compared to a shank of same composition and size not treated in accordance with step (b), andwherein the heat-treated shank has an angle greater than 10 degrees of permanent deformation after torque at 45° of flexion when tested in accordance with ISO Standard 3630-1. 9. The endodontic instrument of claim 8 wherein the fatigue life is determined by a cyclic fatigue analysis. 10. The endodontic instrument of claim 9 wherein the heat-treated shank has increased angular deflection compared to a shank of same composition and size not treated in accordance with step (b). 11. The endodontic instrument of claim 8 wherein the fatigue life is determined by a cyclic fatigue analysis based on ISO Standard 3630-2 Dental root-canal instruments—Part 2: Enlargers and ANSI/ADA Specification No. 95, for Root canal enlargers. 12. The endodontic instrument of claim 11 wherein cyclic fatigue revolutions are increased by at least 50%. 13. The endodontic instrument of claim 11 wherein cyclic fatigue revolutions are increased by at least 100%. 14. The endodontic instrument of claim 8 wherein the heat-treating is at a temperature from 300° C. up to but not equal to the melting point of the nickel titanium alloy. 15. The endodontic instrument of claim 8 wherein step (b) comprises heat-treating at a temperature dependent on a time period selected for heat exposure. 16. The endodontic instrument of claim 8 wherein step (b) comprises heat-treating the shank in an atmosphere that comprises a gas selected from the group consisting of helium, neon, argon, krypton, xenon, and radon.