Endodontic instruments with pilot tips and parabolic cutting flutes

Abstract

A series of multi-tapered parabolic implements is disclosed for endodontic use. The instruments comprise different sections: a pilot tip, a first portion adjacent the pilot tip and a second portion adjacent the shank. The two portions have different tapers. The tapers of the two different portions blend into each other along a parabola-shaped surface. The pilot tip is radiussed for ease of entry into a root canal with increased safety.

1 . An endodontic file comprising: 
 a round shank having a first diameter;    a tip at the end of the file remote from the shank, said tip having a second diameter which is smaller than said first diameter; and    a tapered flute portion extending between said tip and said shank and having at least one spiral cutting edge throughout the length thereof;    wherein said tapered flute portion has at least two different degrees of taper in different parts of said flute portion; and    wherein the change of taper between said at least two different degrees of the taper is gradual and continuous from the taper of one part of said flute portion to the taper of said different part of said flute portion.    
   
   
       2 . The file of  claim 1  further including a handle affixed to the shank of the file for facilitating the manipulation of the file.  
   
   
       3 . The file of  claim 1  wherein the shank is provided with a latch-grip portion for coupling to a dental handpiece.  
   
   
       4 . The file of  claim 1  wherein a first part of said flute portion, adjacent the tip, is provided with a first fixed degree of taper throughout the extent of said first part and a second part of said flute portion, adjacent the shank, is provided with a second fixed degree of taper which is less than the taper of the first part; and wherein the change of taper from one part to another follows a radiussed curve.  
   
   
       5 . The file of  claim 4  wherein the tapers of the first and second parts of the flute portion are in a selected ratio with respect to each other.  
   
   
       6 . The file of  claim 5  wherein said ratio is within a range of three to six.  
   
   
       7 . A set of endodontic files, each corresponding to the file of  claim 4 , wherein the taper of the first part of the flute portion varies from file to file in said set.  
   
   
       8 . The set of endodontic files according to  claim 7  wherein the range of variation from file to file of taper of the first part of the flute portion is from 0.06 mm/mm to 0.12 mm/mm.  
   
   
       9 . The set of endodontic files according to  claim 8  wherein the degree of taper of the second part of the flute portion varies from file to file inversely to the variation of degree of taper in the first part of the flute portions of said set.  
   
   
       10 . The set of endodontic files in accordance with  claim 8  wherein the taper of the second part of said flute portion increases from 0.01 to 0.04 mm/mm as the taper of the first part of said flute portion diminishes from 0.12 to 0.06 mm/mm.  
   
   
       11 . The endodontic file of  claim 1  wherein the degree of taper at the tip of said file changes to the taper angle adjacent the shank following a parabolic curve.  
   
   
       12 . The endodontic file of  claim 1  wherein the change of taper from the tip to the shank portion occurs over a radius.  
   
   
       13 . The endodontic file of  claim 1  further comprising a pilot tip at the end of the file remote from the shank for guiding the file along the root canal of the tooth.  
   
   
       14 . The endodontic file of  claim 13  wherein said pilot tip and the portion of the file adjacent said tip have corresponding diameters which limit the penetration of the file into a prepared root canal.  
   
   
       15 . The endodontic file of  claim 13  wherein said pilot tip is fully radiussed over 180° across the axis of the pilot tip.  
   
   
       16 . The endodontic file of  claim 15  wherein said pilot tip presents a smooth surface at the forward end of the file to avoid ledging as the file approaches the apical end of the root canal.  
   
   
       17 . The endodontic file of  claim 15  wherein the pilot tip varies in length from one file to another, the pilot tip length being shorter than 1 mm. for pilot tips with narrower diameters and longer than 1 mm. for files with relatively larger pilot tip diameters.  
   
   
       18 . An endodontic implement for use in preparation of a root canal for the filling of said root canal in a human tooth, said implement comprising: 
 a round shank and a cutting flute portion having a proximal end adjacent the shank and a distal end remote from the shank, the distal end of the cutting flute portion including a pilot tip extending from the adjacent cutting flute portion;    wherein said cutting flute portion is tapered from the shank to the distal end thereof;    wherein the cutting flute portion comprises an α section which is remote from said shank and a β section which is between the a section and the shank, the α and β sections having different degrees of taper with the degree of taper varying gradually and continuously from one section to the other; and    wherein said pilot tip is fully radiussed through an angle of 180° about the pilot tip axis.    
   
   
       19 . The endodontic file of  claim 18  wherein said pilot tip presents a smooth surface at the forward end of the file to avoid ledging as the file approaches the apical end of the root canal.  
   
   
       20 . The endodontic file of  claim 18  wherein the taper of the α section varies along a parabolic curve.  
   
   
       21 . The endodontic file of  claim 17  wherein said pilot tip is approximately 1 mm. in length.  
   
   
       22 . The endodontic file of  claim 17  wherein said pilot tip length varies from 0.25 mm. for a file of 0.01 mm. diameter to 1.0 mm. for a file of 1.1 mm. diameter.