U.S. patent application number 12/804956 was filed with the patent office on 2010-12-09 for method of producing cut blades for instruments used in root canal treatment.
Invention is credited to Jean-Marie Badoz, Franck Poncot.
Application Number | 20100311010 12/804956 |
Document ID | / |
Family ID | 35614688 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100311010 |
Kind Code |
A1 |
Badoz; Jean-Marie ; et
al. |
December 9, 2010 |
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.
Inventors: |
Badoz; Jean-Marie; (Doubs,
FR) ; Poncot; Franck; (Besancon, FR) |
Correspondence
Address: |
Gary M. Cohen, Esq.;Strafford Building Number Three
Suite 300, 125 Strafford Avenue
Wayne
PA
19087-3318
US
|
Family ID: |
35614688 |
Appl. No.: |
12/804956 |
Filed: |
August 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11242502 |
Oct 3, 2005 |
7785174 |
|
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12804956 |
|
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Current U.S.
Class: |
433/102 ;
83/55 |
Current CPC
Class: |
Y10T 83/06 20150401;
Y10T 29/49567 20150115; B24B 19/04 20130101; A61C 5/40
20170201 |
Class at
Publication: |
433/102 ;
83/55 |
International
Class: |
A61C 5/02 20060101
A61C005/02; B26D 3/00 20060101 B26D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2005 |
FR |
05 05987 |
Claims
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.
Description
RELATED CASE
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/242,502, filed Oct. 3, 2005.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to the field of
endodontic instruments, and more particularly, to a conical blank
and to a method of producing cut blades for instruments used in
root canal treatment.
[0003] Endodontic instruments of this type are mainly composed of a
blade and a shaft. The blade is inserted into the dental cavity to
be treated and requires a high degree of flexibility in order to
follow the path of the root canal in the tooth. A high degree of
mechanical strength is also required in order not to accidentally
break the blade during working of the canal. The blade defines an
active part having a generally conical shape.
[0004] Such blades were initially made of steel. As these blade
were used, however, it became apparent that steel was not
sufficiently flexible and strong to satisfy the demands placed on
the blades, particularly considering the small diameter of such
blades.
[0005] An article by Walia et al., published in the Journal of
Endodontics in July of 1988 (Volume 14, No. 7, pages 346-351),
described the production of endodontic instruments from a
nickel/titanium alloy. In particular, K-type files were made from a
wire of nickel/titanium with a diameter of 0.020 inches (i.e.,
about 0.508 mm), using a method which started directly from a blank
cut in the wire.
[0006] Using the very strong nickel/titanium alloys satisfied the
basic requirements for endodontic applications, but posed a problem
concerning the speed of the machining operation. This, in turn,
posed a problem relative to the cost of manufacturing cut blades
using the traditional grinding techniques employing cylindrical
blanks.
[0007] Endodontic instruments, for example, those known as
Hedstroem files, have for many years been made by machining, in
particular, by grinding. The process begins with a cylindrical
blank, which is brought in front of a grinder. The grinder has a
configuration such that machining of the blank produces a groove in
the blank, i.e., a "cutting edge", and provides the instrument with
a desired conicity by virtue of the combined advancement of the
blank in front of the grinder, and of rotation of the blank about
its axis. Such instruments are described, for example, in standard
ISO 3630.
[0008] Methods for producing blades having one or more cutting
edges are known, in particular, from U.S. Pat. No. 5,527,205, U.S.
Pat. No. 5,628,674 and U.S. Pat. No. 5,655,950, which describe the
use of cylindrical blanks formed of alloys of at least 40% titanium
and about 50% nickel, and having a diameter of less than 0.07
inches. The blades obtained by the disclosed methods have at least
one channel cut in a helical formation, in a single pass (i.e.,
displacement) in front of the grinder. The disclosed methods are
said to obtain blades which are free from defects, and without
deformation of the metal. U.S. Pat. No. 5,527,205 and U.S. Pat. No.
5,655,950 additionally specify that at least 25% of the diameter of
the cylindrical blank is removed from the portions of the blade
which are to perform the greatest amount of cutting.
[0009] Such processes for producing conical endodontic instruments
from a cylindrical blank were known at the time the
above-identified patents were filed. For example, such methods were
disclosed by Sylvie Yguel Henry, in a thesis presented in Nancy,
France on Jul. 6, 1988, and by Marie-Christine Spohr, in a thesis
presented in Nancy, France on Apr. 29, 1987. Such production
methods were also discussed by Alain Cavalli, in a thesis presented
in Marseilles, France on Mar. 29, 1982.
[0010] Producing cut blades from a cylindrical blank, whether
formed of steel or formed of a nickel/titanium alloy, entails
considerable difficulty in obtaining the overall conical shape of
the cut blade. This conicity can vary from one piece to another,
and in all cases, portions of the cut blade will have a reduced
cross-section, which then requires a substantial removal of
material by abrasion.
[0011] For portions of the cut blade which have a greater diameter,
closer to the diameter of the cylindrical blank, the cutting speed
can be more rapid. This, however, results in a differential removal
of material along the cut part, which in turn poses various
technical problems resulting in a considerable length of time for
the production of the machined piece. This then results in a high
cost for the production of each endodontic instrument.
[0012] Consequently, it is the object of the present invention to
improve the speed of production for cut blades usable in the
endodontic field, and more particularly, to solve this principal
difficulty in association with the production of instruments made
of nickel/titanium.
SUMMARY OF THE INVENTION
[0013] The present invention generally relates to a blank for use
in producing an endodontic instrument by grinding, and to a method
for producing an endodontic instrument provided with at least one
helical cutting edge, using such a blank. The blank has a
cylindrical portion, and a generally conical portion which is to be
machined to form the active part of the final endodontic
instrument. The 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.
[0014] Use of the blank of the present invention makes it possible
to avoid the lengthy machining of the excess material, i.e., the
material situated above the envelope of the desired endodontic
instrument, particularly at the thinner end portions of the
instrument. Along these thinner, tapered end portions, over 60% of
the material associated with prior cylindrical blanks can in some
cases have to be removed during the grinding process. In accordance
with the present invention, the amount of material to be removed by
the grinding process is significantly reduced.
[0015] As a result, the principal advantage of a blank having a
generally conical portion, and of a method for machining such a
blank, in accordance with the present invention, is improvement of
the speed of production of the endodontic instruments which are
produced from such blanks. This is particularly so for the
production of instruments made from materials which are strong and
difficult to machine, of which a representative example is
nickel/titanium alloys. Improvement of the speed of production
logically translates into a reduction in the cost of manufacture of
the instrument.
[0016] Other characteristics and advantages of the present
invention will become clear from the description of non-limiting
examples which follows, with reference to the following
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an elevational view of a conical blank of the
present invention, before machining.
[0018] FIG. 1A is a cross-sectional view of the blank shown in FIG.
1, taken along the line A-A.
[0019] FIG. 1B is a cross-sectional view of the blank shown in FIG.
1, taken along the line B-B.
[0020] FIG. 2 is an elevational view of the conical blank shown in
FIG. 1, after machining.
[0021] FIG. 2A is a cross-sectional view of the blank shown in FIG.
2, taken along the line A-A.
[0022] FIG. 2B is a cross-sectional view of the blank shown in FIG.
2, taken along the line B-B.
[0023] FIG. 3A is an elevational view of a conical blank having
three different conicities, before machining.
[0024] FIG. 3B is an elevational view of the conical blank shown in
FIG. 3A, after machining.
[0025] FIG. 4A is an elevational view of a conical blank having a
variable conicity, for producing an instrument with a concave
active part, before machining.
[0026] FIG. 4B is an elevational view of the conical blank shown in
FIG. 4A, after machining.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Apparatus capable of cutting cylindrical blanks to form
instruments, and more particularly, to form blades that can be used
in the field of endodontics, are known. For example, the
above-mentioned U.S. Pat. No. 5,527,205, U.S. Pat. No. 5,628,674
and U.S. Pat. No. 5,655,950 describe an apparatus having a fixing
device for holding the cylindrical blanks, and means for displacing
the blanks in rotation and in translation in front of a grinder to
form helical grooves in the blanks, and a blade that can be used
for dental care.
[0028] In accordance with the present invention, a conical blank is
cut with a machine which includes the following main components. A
device is provided for loading the blanks in a hopper, and for
bringing blanks which are to be machined to a working zone. A
spindle is provided for receiving a blank, and for holding the
blank during machining. A machining grinder is provided for cutting
the blank which is driven in a movement perpendicular to the axis
of the spindle. A guide is provided substantially opposite to the
grinder, which operates to hold the blank during its machining, and
which is displaced symmetrically relative to the grinder in
relation to the axis of the spindle. A motorized drive is provided
for rotating the blank about its axis, and for displacing the blank
in a direction of advancement during the cutting procedure.
Finally, a device is provided for unloading the machined piece.
[0029] In particular, the machining grinder has an axis of rotation
which is parallel to the axis of the spindle, or which is included
in a vertical plane parallel to the axis of the spindle. The axis
of the grinder forms an angle with respect to a horizontal axis
that varies as a function of the shape of the instrument which is
to be obtained after cutting.
[0030] In accordance with the present invention, and referring to
FIG. 1, a blank for producing an endodontic instrument has a
cylindrical portion 1 and a generally conical portion 2. The
cylindrical portion 1 is fixed in the spindle of the machining
apparatus, and is held along part of its length during machining.
The generally conical portion 2 is machined during displacement of
the blank in front of the grinder, and has an overall shape which
approximates, and which is slightly larger than the geometric
envelope of the final shape which is to be given to the active part
of the endodontic instrument after machining.
[0031] FIG. 2 shows the final instrument which is obtained after
cutting the blank which is shown in FIG. 1. The active part 3 of
the instrument, which is the portion of the instrument designed for
preparation of the tooth canal by the practitioner, has several
cutting edges.
[0032] The blank shown in FIG. 1 has a regular, generally conical
portion 2. The conicity of the generally conical portion is
preferably between 2 and 20%. The generally conical portion 2 of
the blank does not exceed the final diameter of the instrument by
more than 20%. In this way, the material to be removed during
machining is reduced to the maximum extent.
[0033] Referring to FIGS. 1A and 1B, relative to FIGS. 2A and 2B,
the material which is removed by machining of the blank is
illustrated with reference to cross-sectional views taken at A-A
and B-B in FIGS. 1 and 2. The illustrated cross-section of the
final instrument (FIGS. 2A and 2B) shows, in this example, three
cutting edges, which are obtained following three grinding
operations for cutting three helical grooves.
[0034] The blank is preferably made from an alloy of titanium and
nickel, although there is nothing which would exclude the use of
steel, or different alloys. The present invention is all the more
advantageous when the alloy used to produce the endodontic
instrument is strong and difficult to machine since, compared to
known techniques using cylindrical blanks, the amount of material
to be removed is significantly reduced.
[0035] As shown in FIG. 2, the final endodontic instrument includes
several helical cutting edges. The method of producing such an
instrument, in accordance with the present invention, includes the
following operations. A blank is provided which, in accordance with
the present invention, has a generally conical portion which is to
be machined, and a cylindrical portion which permits the blank to
be fixed in the supporting spindle. The blank is then displaced in
a direction of advancement, and is slowly driven in rotation in
front of the rotary grinder, to cut a hollowed-out, helical groove
which develops a first helical cutting edge. This process is
repeated for a number of times corresponding to the number of
cutting edges of the instrument.
[0036] The method for producing an endodontic instrument, in
accordance with the present invention, employs a blank having a
generally conical portion which approximates, and which is slightly
larger than the envelope of the final shape to be given to the
active part of the endodontic instrument after machining, including
the cutting edges of the instrument. The generally conical portion
preferably has a conicity between 2 and 20%, and the diameter of
each section of the generally conical portion does not exceeding
the final diameter of the instrument by more than 20%. The method
of the present invention advantageously uses a blank produced from
an alloy of nickel and titanium to produce the endodontic
instrument.
[0037] The method of the present invention characteristically
employs a speed of advancement of the blank of at least 200 mm per
minute. The speed of advancement can be greater than 300 mm per
minute for the production of an endodontic instrument from a blank
having a conicity of 2%. Such speeds are to be compared with the
much lower speeds of 5 inches per minute, i.e., 127 mm per min,
which are indicated in the above-mentioned U.S. Pat. No. 5,527,205,
U.S. Pat. No. 5,628,674 and U.S. Pat. No. 5,655,950.
[0038] The speed of advancement, combined with the speed of
rotation of the blank about its axis, determines the pitch of the
helix which is cut in the blank. This pitch can be constant or
variable depending on the type of instrument to be produced. The
machining tool used allows the various essential speeds to be
controlled, namely, the speed of advancement of the blank, the
speed of rotation of the blank along its axis, and the speed of
rotation of the grinder.
[0039] The grinder can be inclined to produce different groove
forms in the blank. The characteristics of the usable grinders can
vary depending on the material of the blank and the type of
instrument to be produced. For example, it is possible to use
diamond grinders, vitrified grinders, etc.
[0040] By varying the adjustable parameters of the apparatus, a
wide variety of endodontic instruments can be produced, and this
can be done at very high speeds when compared to known techniques.
The process of the present invention makes it possible to remove
material in a summary fashion which is relatively fast, and which
can even be an approximation of the final shape which is to be
developed, if desired, with any fine machining then being performed
on a separate apparatus.
[0041] In accordance with the present invention, instruments of
different shapes can be produced. For example, and referring to
FIG. 3A, it is possible to cut a blank 4 which has three different
conicities 5, 6 and 7 extending along the generally conical portion
2. FIG. 3B shows the endodontic instrument which is obtained after
machining, as previously described. In this illustration, the
envelope 8 of the initial blank has been shown, surrounding the
active part 3, in order to show that the material removed by
grinding is very limited in volume, which in turn permits a very
rapid machining speed.
[0042] FIG. 4A illustrates another alternative embodiment blank
which can be used in accordance with the present invention. The
blank of FIG. 4A can be used to produce an instrument which is
tapered, and optionally smooth, having, for example, an active part
3 with a concave shape, as is shown in FIG. 4B. For producing this
type of instrument, the generally conical portion of the blank
represented in FIG. 4A can have a regular conicity or a variable
conicity with a concave portion 9 close to that of the final
instrument.
[0043] Numerous other blanks can be employed, in addition to the
above-described, alternative embodiments. The length of the
cylindrical portion, and of the generally conical portion, can vary
relative to one another without departing from the scope of the
present invention. Diverse shapes can also be designed, and the
method of the present invention permits an extensive range of
endodontic instruments to be obtained.
[0044] The method of the present invention can also be used with
various apparatus having means for holding the blank, for placing
the blank in the spindle, and for removing the machined part from
the apparatus after it has been machined, once again, without
departing from the scope of the present invention. The same applies
to the motors and to the peripheral equipment which is used to
allow the machining tool to operate optimally.
[0045] The grinder which is used to permit abrasion of the blank,
to produce the helical grooves in the blank, can turn at different
speeds. As an example, a speed of about 5500 revolutions per minute
can be used for this. The grinder can further employ different
abrasives, provided the resulting cutting is effective and ensures
the highest possible speed of advancement of the blank.
[0046] The speed of advancement of the blank is generally the
factor which limits the speed of production of the instrument. The
speed of rotation of the blank about its axis can also vary within
quite a wide range, depending on the instrument which is desired,
on the efficacy of the grinding procedure, and on the speed of
advancement of the blank. The several parameters governing the
production of the instrument will logically vary depending on the
material which is used to produce the blank.
[0047] After the desired instrument has been obtained, various
unloading devices can be used to discharge the instrument which has
been produced. The unloading device which is used can, if desired,
be connected to a finishing and packaging line in order to permit
maximum automation in serial production.
[0048] It will be understood that the present invention is not
limited to the embodiments which have been described and
illustrated, by way of example, and will instead further
encompasses all technical equivalents and their combinations.
* * * * *