Method of producing cut blades for instruments used in root canal treatment

Abstract

A blank for use in producing an endodontic instrument using a grinding technique includes a cylindrical portion, and a generally conical portion which is to be machined by the grinding technique to form the active part of the endodontic instrument. The generally conical portion of the blank approximates, and is slightly larger than the envelope of the final shape given to the active part of the endodontic instrument after machining. A method is also provided for producing an endodontic instrument having at least one helical cutting edge using the blank.

1 . An article of manufacture formed from a blank by a grinding process and producing an endodontic instrument, wherein the endodontic instrument comprises a cylindrical portion, and an active part including helical cutting edges, and wherein the helical cutting edges of the active part are machined by the grinding process to form a final shape which defines a conical envelope after being machined which approximates and which is smaller than conical portions of the blank which forms the article of manufacture. 
     
     
         2 . The article of manufacture of  claim 1  wherein the conical envelope has a conicity of between 2 and 20%. 
     
     
         3 . The article of manufacture of  claim 1  wherein the conical envelope has a plurality of sections, and wherein the sections have at least two different conicities. 
     
     
         4 . The article of manufacture of  claim 1  wherein the conical envelope has at least one concave portion. 
     
     
         5 . The article of manufacture of  claim 1  wherein the blank is formed of steel. 
     
     
         6 . The article of manufacture of  claim 1  wherein the blank is formed of an alloy of nickel and titanium. 
     
     
         7 . An article of manufacture producing an endodontic instrument by a grinding process, and comprising a cylindrical portion and a generally conical portion which is machined by the grinding process to form an active part of the endodontic instrument;
 wherein, in a first state, the article of manufacture is a blank including the conical portion which forms the active part, and wherein the conical portion has a shape which defines a first envelope;   wherein, in a second state, the active part has helical cutting edges formed in the conical portion, wherein the helical cutting edges of the active part have a shape which defines a second envelope; and   wherein the second envelope defined by the helical cutting edges approximates and is smaller than the first envelope defined by the conical portion.   
     
     
         8 . The article of manufacture of  claim 7  wherein the first envelope is a conical envelope, and wherein the second envelope is a conical envelope. 
     
     
         9 . The article of manufacture of  claim 8  wherein the first envelope has a diameter, and wherein the second envelope has a corresponding diameter which is reduced from the diameter of the first envelope. 
     
     
         10 . The article of manufacture of  claim 9  wherein the corresponding diameter of the second envelope is not reduced from the diameter of the first envelope by more than 20%. 
     
     
         11 . The article of manufacture of  claim 8  wherein the first envelope has a circumference, and wherein the second envelope has a corresponding circumference which is reduced from the circumference of the first envelope. 
     
     
         12 . The article of manufacture of  claim 11  wherein the corresponding circumference of the second envelope is not reduced from the circumference of the first envelope by more than 20%. 
     
     
         13 . The article of manufacture of  claim 7  wherein the second envelope has a conicity of between 2 and 20%. 
     
     
         14 . The article of manufacture of  claim 7  wherein the second envelope has a plurality of sections, and wherein the sections have at least two different conicities. 
     
     
         15 . The article of manufacture of  claim 7  wherein the second envelope has at least one concave portion. 
     
     
         16 . The article of manufacture of  claim 7  wherein the blank is formed of steel. 
     
     
         17 . The article of manufacture of  claim 7  wherein the blank is formed of an alloy of nickel and titanium. 
     
     
         18 . A method for producing an endodontic instrument having at least one helical cutting edge, comprising the steps of:
 providing a blank having a cylindrical portion for fixing the blank in a supporting spindle, and a generally conical portion which is to be machined by a grinding process to form an active part of the endodontic instrument, wherein the conical portion of the blank has a shape which defines a first envelope;   cutting a hollowed-out, helical groove in the conical portion of the blank while displacing the blank in a direction of advancement and slowly rotating the blank in front of a rotary grinder, developing a helical cutting edge in the active part of the endodontic instrument; and   repeating the cutting step for a plurality of times corresponding to a selected number of helical cutting edges for the endodontic instrument, forming the helical cutting edges of the active part in a final shape which defines a second envelope which approximates and which is smaller than the first envelope after being machined.   
     
     
         19 . The method of  claim 18  which further includes the steps of forming the first envelope as a conical envelope, and forming the second envelope as a conical envelope. 
     
     
         20 . The method of  claim 19  wherein the first envelope has a diameter, and which further includes the step of forming the active part of the endodontic instrument so that the second envelope has a corresponding diameter which is reduced from the diameter of the first envelope. 
     
     
         21 . The method of  claim 20  which further includes the step of forming the active part of the endodontic instrument so that the corresponding diameter of the second envelope is not reduced from the diameter of the first envelope by more than 20%. 
     
     
         22 . The method of  claim 19  wherein the first envelope has a circumference, and which further includes the step of forming the active part of the endodontic instrument so that the second envelope has a corresponding circumference which is reduced from the circumference of the first envelope. 
     
     
         23 . The method of  claim 22  which further includes the step of forming the active part of the endodontic instrument so that the corresponding circumference of the second envelope is not reduced from the circumference of the first envelope by more than 20%. 
     
     
         24 . The method of  claim 18  which further includes the step of machining the cutting edges while cutting the helical groove in the conical portion of the blank so that the helical cutting edges have a final shape which is defined by the second envelope. 
     
     
         25 . The method of  claim 18  which further includes the step of providing the conical portion with a conicity of between 2 and 20%. 
     
     
         26 . The method of  claim 18  wherein the conical portion of the blank has a plurality of sections, and which further includes the step of providing the plurality of sections with at least two different conicities. 
     
     
         27 . The method of  claim 18  which further includes the step of forming the blank from steel. 
     
     
         28 . The method of  claim 18  which further includes the step of forming the blank from an alloy of nickel and titanium. 
     
     
         29 . The method of  claim 18  which further includes the step of advancing the blank which is displaced in the direction of advancement at a speed of at least 200 mm per minute.