Endodontic instrument and procedure

A kit of endodontic instruments for use in root canal therapy wherein each instrument comprises an elongate blade having a proximate end and an opposite distal end, and with the blades of the instruments in the kit respectively having progressively increasing tapers. The kit is employed to fill an extirpated root canal with gutta percha, and instruments of progressively increasing taper are used in sequence during the obturation procedure so as to control the compaction of the gutta percha points in the canal.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the field of endodontics, and 
more particularly to a method of applying a filler material in an 
endodontically prepared root canal. 
Root canal therapy is a well-known procedure wherein the crown of a 
diseased tooth is opened so as to permit the canal to be cleaned and then 
filled. More particularly, after the crown is opened so as to expose the 
root canal, a series of very delicate, flexible, finger-held instruments 
or files are used to extirpate or clean out and shape the root canal, and 
each file is manually rotated and reciprocated in the canal by the 
dentist. Files of increasingly larger diameter are used in sequence, to 
achieve the desired cleaning and shaping. When the canal is thus prepared, 
it is obturated or filled with a filling material, which typically 
comprises a waxy, rubbery compound known as gutta percha. 
In one traditional method of obturating a root canal, referred to as to as 
the warm gutta percha vertical compaction technique, strand-like pieces of 
warm gutta percha, commonly referred to as "points", are inserted into the 
extirpated root canal. The points are then physically compacted by a 
rod-like, blunt ended instrument called a plugger, which is inserted into 
the canal and manipulated into contact with the points to compact the 
material into the canal. 
A set of rod-like pluggers of graduated diameters, but of uniform taper, 
may be employed during the compaction process. More particularly, at least 
one gutta percha point is initially inserted into the lower or apical 
third of the canal, and a plugger of small diameter is then employed to 
crush the point into the canal. Small additional pieces of warm gutta 
percha are then inserted, and the procedure is repeated using pluggers of 
increasing diameter, and so as to obturate the entire canal cavity. 
As an alternative to using warm gutta percha points, it is also known to 
utilize cold gutta percha, which is heated in the canal by means of a 
heated spreader, which has a pointed end which is able to penetrate into 
the gutta percha and heat the material prior to being compacted by the 
plugger. 
A potential problem associated with the either the warm or cold gutta 
percha vertical compaction technique is the risk that the forward end of a 
plugger, or the gutta percha, can be forced past the apex of the canal. 
Also, it is easier for the gutta percha to flow downwardly toward the 
apex, rather than laterally, and thus the complete filling of the canal in 
the lateral direction may not be achieved. It is also possible that the 
gutta percha can flow upwardly between the plugger and the wall of the 
canal, and flow out from the upper canal opening, rather than flowing 
downwardly and laterally to fill the canal. 
A further problem associated with the known vertical compaction technique 
is the fact that a substantial portion of the crown of the tooth must be 
removed and widely flared in order to provide sufficient space for the 
pluggers and spreaders to get around the curves in the canal and reach 
substantially to the apex of the canal. This can severely weaken the crown 
of the tooth, and can result in the fracture and complete loss of the 
tooth. 
It is accordingly an object of the present invention to provide a kit of 
obturating instruments, and a novel process utilizing such instruments, to 
perform a vertical compaction procedure, and which avoids the above noted 
problems and disadvantages of the prior art techniques. 
SUMMARY OF THE INVENTION 
The above and other objects and advantages of the present invention are 
achieved in the embodiment illustrated herein by the provision of a kit of 
endodontic obturating instruments, with each of the instruments comprising 
an elongate blade having a proximate end and an opposite distal end, and 
with the blades of the instruments respectively having progressively 
increasing tapers. The blade of each of the instruments preferably is of 
circular cross-sectional outline and has a smooth, non-fluted exterior 
surface, and the distal end of the blade of each instrument comprises a 
blunt transverse end surface. Also, the blade of each of the instruments 
preferably comprises an alloy of nickel and titanium so as to provide a 
high degree of flexibility and resistance to breakage and wear. 
In accordance with the endodontic procedure of the present invention, the 
root canal is first extirpated or cleaned, by successively inserting a 
plurality of tapered files in the canal and manipulating each file in the 
canal. Files of progressively increasing diameter are employed, and so as 
to form the canal into a generally conical configuration which includes a 
relatively wide crown portion and an apex at the inner end of the canal. 
At least one gutta percha point is inserted into the extirpated root 
canal, and the distal end of the blade of a selected one of the kit of 
obturating instruments is then introduced into the root canal so as to 
engage and compact the gutta percha point toward the apex of the canal. 
The selected obturating instrument has a taper which is greater than the 
taper of the extirpated conical root canal, and so that the blade of the 
obturating instrument engages the crown portion of the root canal, and the 
distal end thereof is precluded from reaching the apex of the canal. The 
engagement of the blade with the crown portion of the canal closes the 
upper end of the canal and thus assures that the gutta percha flows 
downwardly toward the apex and not upwardly and out of the canal. Also, by 
selecting the taper of the plugger, the compaction of the gutta percha can 
be controlled in the apical region of the canal so as to not appreciably 
flow through the apex. 
Typically, the endodontic procedure will include the further subsequent 
steps of inserting an additional gutta percha point into the extirpated 
root canal above the previously compacted point, and then inserting the 
distal end of the blade of a second obturating instrument from the kit and 
which has a taper greater than that of the blade of the previously 
inserted instrument. The blade of the second instrument thus engages and 
forces the additional gutta percha point toward the apex of the canal, and 
the blade of the second instrument engages the crown portion of the root 
canal and again closes the canal so that the distal end of the blade of 
the instrument is precluded from reaching into the canal to the extent 
reached by the blade of the first mentioned obturating instrument. Thus 
the compaction of the additional gutta percha can be controlled by 
selecting the taper of the second instrument. 
Preferably, the blade of each of the obturating instruments, and the shank 
of each of the files is composed of an alloy comprising at least about 40% 
titanium and at least about 50% nickel. This composition provides a high 
degree of flexibility, and thus permits the instruments to pass around the 
curves in the canal, even in the case of severely curved canals, without 
requiring the removal and wide flaring of the crown portion of the canal. 
Thus, the procedure may be performed without unduly weakening the crown of 
the tooth. The use of a nickel-titanium alloy also reduces the risk of 
breakage and wear, as compared to conventional stainless steel materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In performing root canal therapy, the crown of the tooth is initially 
opened, and the root canal is extirpated or cleaned. As illustrated in 
FIG. 1, the extirpation is conducted by successively inserting a plurality 
of tapered files 10 in the canal, and manipulating each file by 
simultaneous rotation and axial reciprocation. Files of progressively 
increasing diameter are used in sequence, and so as to form the canal into 
a general conical (albeit curved) configuration, and including a 
relatively wide crown portion and an apex at the inner end of the root 
canal. 
Endodontic files of the described type are commonly supplied to the 
clinician in kits which comprise several files of increasing diameter. In 
particular, and in accordance with ANSI/ADA Specification No. 28-1988, 
files are provided in diameters which range from 0.08 mm at the tip (size 
08) to 1.40 mm at the tip (size 140), and the files are provided in kits 
which contain a number of files of increasing diameter so that the files 
from a particular kit may be used in sequence by the clinician in 
accordance with the requirements of the particular canal being cleaned. 
Each file 10 comprises a metallic shank 12, which typically has a length of 
about 30 mm, and a conventional handle 14 is mounted at the proximate end 
of the shank for engagement between the thumb and forefinger of the 
dentist during the manipulation thereof. 
The portion of the shank 12 immediately below the handle 14 is cylindrical 
and has a diameter of between about 0.5 and 1.6 mm, and this shank portion 
includes calibrated depth markings 15 of conventional design. The shank 
further includes an opposite distal or pilot end, and a working length 
which is defined adjacent the pilot end. The working length is preferably 
slightly tapered toward the pilot end at an included angle of between 
about 1/2.degree. and 4.degree.. 
The working length of the illustrated embodiment of the file 10 further 
comprises two continuous helical flutes which extend along its length. The 
flutes are preferably machined in the outer surface of the file in the 
manner further described in U.S. Pat. Nos. 4,934,934, and 5,380,200. This 
machining operation may result in the two flutes having a curved concave 
wall when viewed in transverse cross-section, and a helical land which is 
positioned between axially adjacent flute sections. Alternatively, a 
machining operation may be employed which produces a triangular or 
quadrangular cross-section (not shown). The configuration and structure of 
the preferred embodiment of the file is further described in the two 
above-referenced patents and in U.S. Pat. No. 5,106,298, the disclosures 
of which are expressly incorporated herein by reference. 
Preferably, the shank 12 of the file 10 is composed of a nickel-titanium 
alloy which provides increased flexibility and wear resistance, and better 
resistance to breakage, as compared to the more conventional stainless 
steel composition. For example, the alloy may comprise at least about 40% 
titanium and at least about 50% nickel, and as a specific preferred 
example, "55-Nitinol" alloy may be used for the shank and which contains 
54 to 56 weight percent nickel with the balance comprising titanium. 
After the extirpation step is completed, the obturation process is 
commenced, which utilizes a kit of obturating instruments 20a, 20b, 20c, 
20d as illustrated in FIG. 2. More particularly, each of the obturating 
instruments, which are commonly called pluggers, comprises an elongate 
rod-like blade 22 having a proximate end 23 and an opposite distal end 24. 
The blade 22 of each of the instruments is of circular cross-sectional 
outline and has a smooth, non-fluted exterior surface. Also, the blades of 
the instruments are tapered from the proximate end toward the distal end, 
with the blades of the instruments in the kit respectively having 
progressively increasing tapers. For example, the blade of each instrument 
in the kit is tapered at an included angle of between about 1/2.degree. 
and 5.degree., and as a specific example, the blade of the instrument 20a 
of the kit may have a taper with an included angle of about 1.degree., the 
second instrument 20b may have a taper of about 2.degree., the third 
instrument 20c may have a taper of about 3.degree., and the fourth 
instrument 20d may have a taper of about 4.degree.. Also, the distal end 
24 of the blade of each of the instruments comprises a blunt transverse 
end surface. 
Preferably, the blade 22 of each of the instruments comprises an alloy of 
nickel and titanium, so as to provide improved flexibility, wear 
resistance, and resistance to breakage, as compared to the conventional 
stainless steel composition. Preferably, the alloy comprises at least 
about 40% titanium and at least about 50% nickel, and most preferably 
"55-Nitinol" alloy as described above is employed. 
The blade 22 of each of the instruments also preferably includes a 
plurality of axially spaced apart depth calibration markings 26 along its 
length, at for example 5 mm intervals, as is conventional. Also, a handle 
28 is mounted at the proximate end of the blade of each of the 
instruments. 
The instruments 20a-20d illustrated in FIG. 2 are commonly referred to as 
"finger" pluggers, since the handles 28 are configured to be engaged 
between the thumb and forefinger of the dentist during use. FIG. 3 
illustrates another kit of obturating instruments 30a, 30b, 30c in 
accordance with the present invention, and which are commonly referred to 
as "hand" pluggers since the handles are sized and configured to be 
engaged by the hand of the dentist in the manner of a pencil. The blades 
of the instruments shown in FIG. 3 respectively have progressively 
increasing tapers in the manner of the instruments shown in FIG. 2. Also, 
the blades of the instruments shown in FIG. 3 have an arcuate medial 
portion and a straight distal end portion, so as to permit the handles to 
be comfortably held in the hand of the dentist. 
As illustrated in FIGS. 4-7, the obturation process is initiated by 
inserting one or perhaps two gutta percha points GP into the extirpated 
root canal, with the points being sized so that they fall into the apical 
third of the canal. One of the obturating instruments is then selected, 
with the selected instrument having a taper slightly greater than that of 
the last file used in the extirpation of the canal, and the distal end 24 
of the blade 22 of the selected instrument is then inserted into the 
canal, so that the blunt end surface of the blade engages the gutta 
percha. An axial force is then applied to the instrument, so as to force 
the gutta percha toward the apex of the canal. Since, the selected 
obturating instrument has a taper which is greater than the taper of the 
extirpated conical root canal, the blade 22 engages the crown portion of 
the root canal as indicated at A in FIG. 5 when the blade is inserted a 
predetermined distance, and such that the distal end 24 is precluded from 
reaching the apex of the canal. The engagement at the point A also closes 
the upper end of the canal and thus assures that the gutta percha flows 
downwardly toward the apex and not upwardly and out of the canal. Also, 
the gutta percha is forced laterally, so as to provide for the complete 
filling of the canal in the lateral direction. 
The instrument is then withdrawn, and one or more additional points of 
gutta percha are inserted into the canal as illustrated at GP' in FIG. 6. 
The distal end of the blade 22' of a second obturating instrument, which 
has a taper greater than that of the first instrument, is inserted into 
the root canal so as to engage and force the additional gutta percha 
points GP' toward the apex of the canal. Here again, the second instrument 
is selected so as to have a taper wherein the blade engages the crown 
portion at the point A as seen in FIG. 7, with the distal end 24' thereof 
being thereby precluded from reaching into the canal to the extent reached 
by the blade of the first instrument. Thus, the proper degree of axial and 
lateral compaction of the additional points may be assured, again without 
flow out of the canal in the upward direction. 
The above steps of inserting additional points and compacting the points 
with instruments of increasing taper is repeated until the canal is 
completely filled with the gutta percha. The crown is then closed in the 
conventional manner, so as to complete the root canal procedure. 
In the drawings and specification, there have been set forth preferred 
embodiments of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.