Method of obturating an extirpated root canal

A method of obturating an extirpated root canal utilizes two types of filler material, one type of which is in the form of a gutta-percha point and the other type of which is a thermoplasticized gutta-percha having a melting temperature of about 15.degree. to 20.degree. C. less than the melting temperature of the gutta-percha point. The steps of the method include the introducing of an initial amount of thermoplasticized gutta-percha in a heated and softened condition into the root canal so that the initial amount fills the bottom of the canal. A gutta-percha point is then positioned within the root canal and another amount of thermoplasticized gutta-percha is introduced in a heated and softened condition into the canal. The thermoplasticized gutta-percha is then manipulated into contact with the portion of the gutta-percha point positioned within the root canal so that the gutta-percha point is fed into and compacted within the root canal with the thermoplasticized gutta-percha. Additional amounts of thermoplasticized gutta-percha are introduced and manipulated into contact with additional gutta-percha points as necessary to fill the root canal with a core of filler material.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates generally to the field of endodontics and 
relates more particularly to processes for filling stripped root canals. 
Known methods of obturating (filling) an extirpated (stripped) root canal 
commonly involve the insertion of strand-like pieces of gutta-percha known 
as points into the root canal and the use of compacting tools known as 
plungers and spreaders to compact the gutta-percha points within the 
canal. Typically, the compacting tools are heated to soften the 
gutta-percha points in the canal and then hand manipulated to 
progressively feed and compact the points in the canal. Additional points 
are fed to the canal as the compacting operation progresses in order to 
fill the canal with gutta-percha. 
Another known method of obturating an extirpated root canal involves the 
insertion of gutta-percha points into the root canal and manipulating the 
shank of a high-speed, rotating instrument into contact with the 
gutta-percha points so that frictional heat generated at the instrument 
shank softens the gutta-percha. With the gutta-percha in a softened 
condition, it is compacted within the canal with manipulations which 
include reciprocating motions of the instrument shank. 
Limitations associated with known obturation methods relate to the general 
difficulty in filling of the root canal with filler material so that any 
voids or fissures associated with the canal wall are filled and the 
utilization of relatively large and/or high-speed rotating instruments to 
compact the material within the canal. Unless an endodontist who performs 
known obturating techniques is highly skilled, all voids and fissures of 
the canal are not always filled satisfactorily. In addition, reciprocating 
motions of a relatively large compacting instrument against filler 
material positioned within a canal increase the possibility that the 
apical foramen will be extruded by the filler material. Moreover, 
utilization of any high-speed rotating instrument within a mouth requires 
a great deal of care to prevent injury to the patient or keep from 
fracturing the instrument. 
It would be desirable to provide a new method for obturating an extirpated 
root canal with a greater likelihood that gutta-percha compacted within 
the root canal conforms to the shape of the wall of the root canal and 
that fissures or similar openings associated with the canal wall are 
completely filled with gutta-percha. 
Another object of the present invention is to provide such a method which 
obviates the use of large and/or high-speed rotating instruments for 
compacting filler material within a root canal. 
More particularly, the present invention is directed to the obturating of 
an extirpated root canal with two types of filler material wherein one 
type of filler material is provided in the form of a gutta-percha point 
having a predetermined melting temperature and wherein the other type of 
filler material is provided in the form of a thermoplasticized 
gutta-percha having a melting temperature of about 15.degree. to 
20.degree. C. less than that of the melting temperature of the 
gutta-percha point. Steps in the method include the introduction of an 
initial amount of thermoplasticized gutta-percha in a heated, softened 
condition into the root canal so that the initial amount fills the bottom 
of the canal. At least a portion of the gutta-percha point is then 
positioned into the root canal, and another amount of thermoplasticized 
gutta-percha in a heated, softened condition is introduced into the canal. 
The another amount of thermoplasticized gutta-percha is then manipulated 
into contact with the portion of the gutta-percha point positioned within 
the canal so that the gutta-percha point is fed into and compacted within 
the root canal with the amounts of thermoplasticized gutta-percha. 
Because the thermoplasticized gutta-percha introduced into the canal is a 
fluid in its heated and softened condition, the apical foramen and any 
fissures or voids associated with the canal wall are suitably coated 
and/or filled by the thermoplasticized gutta-percha with no need that 
filler material be forcibly urged, such as by reciprocating motions of a 
compacting instrument, into the canal. Thus, the endodontist performing 
the method of this invention need not possess as high a degree of skill as 
in prior methods in order to satisfactorily fill the root canal, and the 
possibility that the apical foramen will be extruded by filler material is 
reduced by this method. In addition, the heat necessary for softening and 
rendering workable the gutta-percha point material is absorbed by the 
point material from the heat of the softened thermoplasticized material. 
Thus, the method of the invention obviates any need for the manipulation 
of a high-speed rotating instrument within the canal for the purpose of 
generating frictional heat. 
A more complete understanding of the present invention will be had by 
reference to the specification and accompanying drawings wherein like 
numerals refer to like parts throughout.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
There is illustrated in FIG. 1 a tooth 20 having a root canal 22 which has 
been extirpated (stripped) in preparation of an obturating (filling) 
process in accordance with an embodiment of the method of the invention. 
The root canal 22 has been extirpated in accordance with well known 
procedures which remove dead or damaged tissue from the canal 22 in order 
to provide a space 24 for accepting filler material inserted and compacted 
therein. In the depicted tooth 20, there are illustrated fissures 26, 28, 
30 defined within the wall of the root canal 22 which are ordinarily 
difficult to fill by conventional obturating processes. As will be 
apparent herein, by feeding and compacting two types of filler material 
within the root canal 22 in accordance with the steps of this invention, 
the entire space 24 of the root canal 22 and the fissures 26, 28, 30 
defined along the root canal wall are completely filled with filler 
material. 
With reference to FIG. 2, there is shown an exemplary instrument 32 of a 
type used to spread and compact filler material within the root canal 
space 24. The instrument 32 includes a rotatable shank 34 having a working 
portion 36 extending along a substantial portion of the shank length and 
terminating at a pilot tip 38. When performing the obturating method 
described herein, the instrument 32 is rotated within a root canal at 
relatively slow speeds. To this end, the portion of the shank 34 above the 
working portion 36 is provided with a fitting which is adapted to mate 
with the chuck 42 of a dental handpiece 44 for powering the rotation of 
the instrument 32 at low speeds or to mate with a handle (not shown) 
facilitating rotation and manipulation of the instrument 32 by hand. 
Although the working portion 36 of the instrument shank 34 may take any of 
a number of forms, the depicted working portion 36 includes at least one 
helical flute 46 extending along the length of the working portion 36 so 
as to provide a downwardly-directed shoulder 48 which spirals along the 
length of the working portion toward the tip 38 thereof. When the shank 34 
is rotated within a root canal in an appropriate direction, filler 
material which comes into contact with the shank 34 is urged by the 
shoulder 48 downwardly toward and off of the tip 38. 
In accordance with the method described herein, two types of filler 
material are used to obturate the canal 22. One type of filler material, 
indicated 50 in FIG. 5, is provided in the form of a strand-like piece of 
gutta-percha, commonly known as a point. Normally, gutta-percha points are 
solid in form at room temperature, e.g., about 24.degree. C., so that heat 
must be applied to the points in order to render the points soft and 
pliable for compaction within a root canal. Although gutta-percha points 
may possess a melting temperature within a relatively broad range, it has 
been found that gutta-percha material possessing a melting temperature of 
no less than about 50.degree. C. is well-suited for use in the obturating 
process described herein. 
Heat is transferred to the gutta-percha point 50 in a manner described 
herein to render the point soft and workable within the root canal 22. 
Once softened to a workable condition, the gutta-percha of the point 50 
may be compacted within the root canal 22 by the instrument 32. As the 
lower portion of the gutta-percha is compacted by the instrument 32, the 
upper end of the point 50 is drawn downwardly into the canal 22 so that 
the material of the point 50 is continually fed to the site at which the 
material is compacted. 
The second type of filler material, indicated 52 in FIG. 2, is a 
thermoplasticized gutta-percha having a melting temperature which is about 
15.degree. to 20.degree. C. lower than that of the gutta-percha point 
material described above. An exemplary filler material found to be 
well-suited as the thermoplasticized gutta-percha for the process 
described herein is available under the trade designation Ultrafil from 
Hygenic Corp. of Akron, Ohio. Physical properties, including the melting 
temperatures, of Ultrafil material are discussed in an article entitled 
"Changes in the Physical Properties of the Ultrafil Low-Temperature 
(70.degree. C.) Thermoplasticized Gutta-percha System" appearing on pages 
517-521 in the November, 1989 issue of the Journal of Endodontics and 
which is incorporated herein by reference. 
As will be apparent herein, the thermoplasticized gutta-percha amount 52 is 
worked with the rotating shank 34 of the compacting instrument 32 in order 
to compact the amount 52 within the canal. However, Ultrafil and like 
materials are relatively firm at room temperature. Consequently, such 
filler material must be heated in order to render the material soft and 
pliable. Such heating may be effected external to the root canal by 
placing the material within a suitable container and by either rotating an 
instrument within the container (to generate frictional heat) or by 
applying heat to the outside of the container. 
For introduction of thermoplasticized gutta-percha 52 into a root canal, 
the thermoplasticized gutta-percha, after being heated to a softened 
condition, is applied to the shank 34 of the compacting instrument so as 
to coat the shank 34 as depicted in FIG. 2, and then introduced into the 
canal by inserting the coated shank 34 into the canal. The instrument 
shank 32 may be appropriately coated with thermoplasticized gutta-percha 
by simply dipping the shank 32 into a quantity of the softened material 
which, in turn, adheres to the shank 32. 
To perform the obturating process, the coated shank 34 of the instrument 32 
is inserted into the root canal 22 as illustrated in FIG. 3 so that the 
shank tip 38 is positioned adjacent the apical foramen 54. The shank 34 is 
then rotated about its longitudinal axis in the direction of the arrow 53 
to urge the amount 52 of thermoplasticized gutta-percha downwardly and off 
of the shank tip 38. Once the amount 52 has been urged off of the shank 34 
so that the bottom of the canal 22 is filled with the amount 52 as 
illustrated in FIG. 4, the shank 34 is removed from the canal 22. 
An advantage provided by the aforedescribed step of introducing an amount 
52 of thermoplasticized gutta-percha into the canal 22 relates to the 
conformance of the amount 52 to the apical portion of the canal. In its 
heated and softened condition, the thermoplasticized gutta-percha amount 
52 possesses a relatively low viscosity so that when introduced into the 
bottom of the canal 22, the amount 52 easily flows along the surface of 
the apical foramen 54 so as to completely cover the apical portion of the 
canal 22. Thus, there is no need to urge filler material downwardly into 
the canal 22 with reciprocating or "chopping" motions of a compacting tool 
which may otherwise be required with a less "fluid" filler material and 
which increases the likelihood of extrusion of the apical foramen with the 
filler material. 
Next, the gutta-percha point 50 is positioned within the root canal 22 as 
illustrated in FIG. 5 so that the lower end of the point 50 is positioned 
adjacent the bottom of the canal 22. An additional amount, indicated as 
64, of thermoplasticized gutta-percha is then applied to the shank 34 of 
the compacting instrument 32 in a heated and softened condition, and the 
coated shank 34 is inserted into the root canal 22 as illustrated in FIG. 
5 so that the shank tip 38 is positioned adjacent the apical foramen 54. 
The instrument 32 is then energized to rotate the shank 34 and 
appropriately manipulated with the hand so that the amount of 
thermoplasticized gutta-percha 64 which coats the shank 34 contacts the 
lower portion of the point 50. As the shank 34 continues to be rotated and 
the filler materials amounts 50 and 64 contact one another, heat from the 
thermoplasticized gutta-percha amount 64 is absorbed by the gutta-percha 
of the point 50 so that the point 50, and in particular the lower portion 
of the point 50, becomes softened and mixes with the thermoplasticized 
gutta-percha 52. Satisfactory mixing of the thermoplasticized gutta-percha 
with the point material may be effected by rotating the instrument shank 
34 as slowly as 25 rpm. 
As the mixing of the material amounts 50 and 64 continues, the shank 34 is 
continually manipulated to work the softened material mix into a desired 
region of the canal space 24, and the upper portion of the point 50 is 
drawn downwardly into the canal 22 where it is compacted with the 
thermoplasticized gutta-percha. Hand manipulations of the instrument 32 
which move the shank 34 along its longitudinal axis in a reciprocating 
manner may be helpful in directing the softened material mix into a 
desired region of the canal space 24. Upon complete mixing or displacing 
of the point 50 with the amount of thermoplasticized gutta-percha 64 as 
illustrated in FIG. 7 so that the filler material mix, indicated as 56, is 
positioned adjacent the bottom of the canal 22, the instrument shank 34 is 
removed from the canal 22. 
With the instrument shank 34 removed from the canal 22, an additional 
gutta-percha point 56 (FIG. 8) is placed within the canal 22 so that the 
lower portion of the point 56 is positioned adjacent the filler material 
mix 56 previously compacted within the canal 22. An additional amount 70 
(FIG. 8) of heated thermoplasticized gutta-percha is then applied to the 
shank 34 of the instrument 32, and the shank 34 is then inserted and 
rotated within the canal 22. By appropriate manipulation of the rotating 
shank 34 so that the amount 70 of thermoplasticized gutta-percha engages 
the point 58, the lower portion of the second point 58 becomes softened 
and mixes with the amount 70 of thermoplasticized gutta-percha. As the 
point 58 continues to be mixed with the amount 70, the upper portion of 
the point 58 is drawn downwardly into the canal 22, as illustrated in FIG. 
9. Meanwhile, the shank 34 continues to be manipulated to compact the 
mixed material of the point 58 and amount 70 atop the filler material mix 
56. Upon completion of the compacting and mixing of the point 58 and the 
amount 70 within the canal 22 as illustrated in FIG. 10, the instrument 
shank 34 is removed from the canal 22. 
The steps of inserting a gutta-percha point within the canal 22, applying 
an amount of heated thermoplasticized gutta-percha to the instrument shank 
34, inserting and rotating the shank 34 within the canal 22 to mix and 
compact the gutta-percha point with the thermoplasticized gutta-percha 
within the root canal 22 are thereafter repeated as necessary until the 
root canal space 24 is completely filled with filler material as 
illustrated in FIG. 11. The filled root canal may thereafter be finished 
by conventional techniques. 
Another advantage provided by the aforedescribed obturating process relates 
to the filling of the fissures 26, 28, 30 and similar openings defined in 
the wall of the extirpated root canal 22. More specifically, as the filler 
materials are mixed and worked against the wall of the root canal 22, the 
filler material of the mix flows within so as to completely fill the canal 
wall fissures 26, 28, 30. It is believed that such a complete filling of 
the fissures 26, 28, 30 is effected as the thermoplasticized gutta-percha, 
which is more "fluid" in its heated and softened condition than is the 
softened material of the gutta-percha points, forms a perimetal layer 66 
(FIG. 12), comprised primarily of thermoplasticized gutta-percha, about a 
core 68, comprised primarily of gutta-percha point material. Consequently, 
as the perimetal layer 66 of the mixed filler material amounts is moved 
along the root canal wall, the "fluid" thermoplasticized gutta-percha 
readily conforms to the shape of the canal wall and flows into the 
fissures 26, 28, 30 opening out of the wall. The core 68 of the filler 
material mix subsequently cures to a solid, relatively rigid condition 
within the canal and ensures that the filler material mix which cures 
within the canal 22 is firmly held therein. 
Still another advantage of the aforedescribed process relates to the fact 
that because the heat needed to soften and render workable the 
gutta-percha point material is absorbed by the point material from the 
thermoplasticized gutta-percha amounts, there is no need to generate 
frictional heat or provide extraneous heat within the root canal 22 that 
may threaten injury to the tissues supporting the tooth. Consequently, an 
endodontist may use a smaller and slower-rotating compacting instrument 
when compacting the mix than what otherwise may be required to generate 
frictional heat within the canal 22. Instead and as mentioned earlier, the 
endodontist may use a manual instrument to work and compact the filler 
materials together. In addition, any need for a larger instrument to 
"chop" point material into a softened condition and heating by the 
friction generated by the instrument within the canal is obviated, and any 
likelihood of injury to the apical foramen 54 or some other region of the 
root canal 22 from instrument-applied pressure is thereby reduced. 
The foregoing detailed description is given primarily for understanding of 
the invention and no unnecessary limitations are to be understood 
therefrom for modifications will become obvious to those skilled in the 
art upon reading this disclosure and may be made without departing from 
the spirit of the invention and the scope of the appended claims.