ENDODONTIC ROTARY INSTRUMENTS MADE OF SHAPE MEMORY ALLOYS IN THEIR MARTENSITIC STATE AND MANUFACTURING METHODS
A method for manufacturing a non-superelastic rotary file comprising the steps of: providing a superelastic rotary file having an austenite finish temperature; and heating the superelastic rotary file to a temperature of at least about 300° C. for a time period of at least about 5 minutes to alter the austenite finish temperature thereby forming the non-superelastic rotary file; wherein the altered austenite finish temperature of the non-superelastic rotary file is greater than about 25° C.
1 . A method for manufacturing a non-superelastic rotary file comprising the steps of:
providing a superelastic rotary file having an austenite finish temperature; and
heating the superelastic rotary file to a temperature of at least about 300° C. for a time period of at least about 5 minutes to alter the austenite finish temperature thereby forming the non-superelastic rotary file;
wherein the altered austenite finish temperature of the non-superelastic rotary file is greater than about 25° C.
2 . The method of claim 1 , wherein the altered austenite finish temperature of the non-superelastic rotary file is greater than 30° C.
3 . The method of claim 2 , wherein the altered austenite finish temperature of the non-superelastic rotary file is greater than 37° C.
4 . The method of claim 1 , wherein the heating step, the temperature ranges from about 300° C. to about 600° C.
5 . The method of claim 4 , wherein the heating step, the time period ranges from about 5 minutes and about 120 minutes.
6 . The method of claim 1 , wherein the superelastic rotary file includes a shape memory alloy.
7 . The method of claim 6 , wherein the shape memory alloy includes nickel and titanium.
8 . The method of claim 6 , wherein the shape memory alloy includes a copper based alloy, an iron based alloy or a combination of both.
9 . The method of claim 1 , wherein a ratio of peak torque of the non-superelastic rotary file to the superelastic rotary file is less than about 8:9 at about 25° C.
10 . The method of any of the preceding claims, wherein a ratio of total number of cycles to fatigue of the non-superelastic rotary file to the superelastic rotary file is at least about 1.25:1 at about 25° C.
11 . The method of claim 1 , wherein:
(i) the altered austenite finish temperature of the non-superelastic rotary file is greater than 30° C.;
(ii) the heating step, the temperature ranges from about 300° C. to about 600° C.;
(iii) the heating step, the time period ranges from about 5 minutes and about 120 minutes;
(iv) the superelastic rotary file includes a shape memory alloy, the shape memory alloy includes nickel and titanium.
12 . A method for manufacturing a non-superelastic rotary file comprising the steps of:
providing a non-superelastic wire having an austenite finish temperature greater than about 25° C.;
heating the non-superelastic wire to a manufacturing temperature that is higher that the austenite finish temperature; and
forming flutes, grooves, or a combination of both about the superelastic wire to form a rotary file;
wherein the rotary file is non-superelastic at a temperature that ranges from about 25° C. to about the austenite finish temperature.
13 . The method of claim 12 , wherein the austenite finish temperature of the non-superelastic rotary file is greater than 27° C.
14 . The method of claim 12 , wherein the austenite finish temperature of the non-superelastic rotary file is greater than 37° C.
15 . The method of claim 12 , wherein the heating step, the manufacturing temperature ranges from about 5° C. to about 200° C.
16 . The method of claim 12 , wherein the non-superelastic wire includes a shape memory alloy.
17 . The method of claim 16 , wherein the shape memory alloy includes nickel and titanium.
18 . The method of claim 16 , wherein the shape memory alloy is a nickel-titanium based ternary alloy.
19 . The method of any of claim 18 , wherein the nickel-titanium based ternary alloy of the formula Ni—Ti—X wherein X is Co, Cr, Fe, or Nb.
20 . The method of claim 1 , wherein:
the altered austenite finish temperature of the non-superelastic rotary file is greater than 30° C.;
(ii) the heating step, the temperature ranges from about 300° C. to about 600° C.;
(iii) the superelastic rotary file includes a shape memory alloy, the shape memory alloy includes nickel and titanium; and
(iv) a ratio of peak torque of the non-superelastic rotary file to the superelastic rotary file is less than about 8:9 at about 25° C.